Syntax

The mumax³ input syntax is a subset of Go's syntax, somewhat similar to C. It is case-independent however, so msat is the same as Msat or MSAT.

Defining variables

New variables are declared using :=. Variables have a fixed type, inferred from the declaration's right-hand-side. Assigning to existing variables is done using =. E.g.:

i := 7         // defines a new variable i, type automatically detected to be int
print(i)       // now we can use i
i = 5          // assign new value, don't use ':=' (attempt to re-declare)

str := "hello" // defines str, type automatically is string
//str = 1      // would fail, cannot assign int to string

Arithmetic

Most common arithmetic operations are possible. Also Go's math library and some common constants are available. For raise-to-the-power, pow(x,y) should be used.

x := pi*(3+4)/5
x = pow(x, 3)
x++
y := abs(cbrt(cosh(erf(erfc(gamma(J0(Y0(2))))))))

Control structures

Loops are possible as well:

for i:=0; i<10; i++{
	 print(i)
}

Implicit functions

Some of the API features accept a function as argument (e.g.: RunWhile(func()bool), or all input parameters). In that case, and only in this case, the argument is implicitly converted to a function, which is re-evaluated each time it's needed. E.g.:

value := sin(pi*t)  // value is a float64, RHS evaluated only once
Msat = value        // time-independent Msat

versus:

Msat = sin(pi*t)    // RHS converted to function, re-evaluted every time

Methods

Some of the API instances have methods defined on them. You can call methods on an instance by using '.' as in most object oriented programming languages. E.g.: a material parameter such as Msat has the method SetRegion(int, float) to set the value of the material parameter in a certain region:

Msat.SetRegion(1, 800e3) // Set Msat=520e3 in region 1

Mesh size and geometry

The simulation mesh defines the size of the box around your magnet. It should be set at the beginning of the script. The number of cells should preferably be powers of two, or at least have small prime factors (2,3,5,7). E.g.:

Nx := 128
Ny := 64
Nz := 2
sizeX := 500e-9
sizeY := 250e-9
sizeZ := 10e-9
SetGridSize(Nx, Ny, Nz)
SetCellSize(sizeX/Nx, sizeY/Ny, sizeZ/Nz)

Periodic boundary conditions

Optionally, periodic boundary conditions can be enabled:

SetPBC(5, 0, 0)        // 5 extra images on left and right sides.
SetGridSize(128, 64, 1)
SetCellSize(5e-9, 5e-9, 5e-9)

Setting a nonzero PBC value in a direction enables wrap-around in that direction. The precise value passed determines how many repetitions are seen by the demag field. E.g., in the above example the demag field behaves as if 5 repetitions are present to the left and to the right side. Choosing a large number may cause long initialization time.

Resizing the mesh

The mesh can be changed at any later time in the simulation. This will cause the magnetization to be stretched onto the new mesh if needed, and the geometry and regions to be re-calculated. After resize some cells which had zero magnetization may now fall inside the magnet geometry, they will be initialized to random magnetization.

Setting the geometry

Optionally a magnet Shape other than the full simulation box can be specified. In order to set the geometry, you first need to define a shape.

geometryShape := cylinder(400e-9, 20e-9).RotX(45*pi/180).Transl(1e-6,0,0)
SetGeom(geometryShape)

SetCellSize(float64, float64, float64)

Sets the X,Y,Z cell size in meters

examples: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]

SetGeom(Shape)

Sets the geometry to a given shape

examples: [4] [6] [7] [8] [9] [11] [12] [14]

SetGridSize(int, int, int)

Sets the number of cells for X,Y,Z

examples: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]

SetMesh(int, int, int, float64, float64, float64, int, int, int)

Sets GridSize, CellSize and PBC at the same time

SetPBC(int, int, int)

Sets the number of repetitions in X,Y,Z to create periodic boundary conditions. The number of repetitions determines the cutoff range for the demagnetization.

EdgeSmooth

Geometry edge smoothing with edgeSmooth^3 samples per cell, 0=staircase, ~8=very smooth

examples: [4]

Shapes

A shape is an abstract object which outlines an area in a 3D universe. Shapes are useful for different tasks, e.g.: to define the geometry of a magnet, to define material regions, or to set locally a specific initial magnetization configuration. One can specify primitive shapes, constructed at the origin (box center), and translate/rotate them if needed. All positions are specified in meters and the origin lies in the center of the simulation box. E.g.:

myShape := cylinder(400e-9, 20e-9).RotX(45*pi/180).Transl(1e-6,0,0)
anotherShape := Circle(400e-9).sub(Circle(200e-9))

Cell(int, int, int) Shape

Single cell with given integer index (i, j, k)

methods: Add( Shape ) Intersect( Shape ) Inverse( ) Repeat( float64 float64 float64 ) RotX( float64 ) RotY( float64 ) RotZ( float64 ) Scale( float64 float64 float64 ) Sub( Shape ) Transl( float64 float64 float64 ) Xor( Shape )

examples: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]

Circle(float64) Shape

2D Circle with diameter in meter

examples: [4] [6] [7] [8] [12]

Cone(float64, float64) Shape

3D Cone with diameter and height in meter. The top of the cone points in the +z direction.

Cuboid(float64, float64, float64) Shape

Cuboid with sides in meter

examples: [4]

Cylinder(float64, float64) Shape

3D Cylinder with diameter and height in meter

examples: [4] [5] [6]

Ellipse(float64, float64) Shape

2D Ellipse with axes in meter

examples: [14]

Ellipsoid(float64, float64, float64) Shape

3D Ellipsoid with axes in meter

examples: [4]

GrainRoughness(float64, float64, float64, int) Shape

Grainy surface with different heights per grain with a typical grain size (first argument), minimal height (second argument), and maximal height (third argument). The last argument is a seed for the random number generator.

ImageShape(string) Shape

Use black/white image as shape

examples: [4]

Layer(int) Shape

Single layer (along z), by integer index starting from 0

examples: [4] [13] [14]

Layers(int, int) Shape

Part of space between cell layer1 (inclusive) and layer2 (exclusive), in integer indices

examples: [4]

Rect(float64, float64) Shape

2D rectangle with size in meter

examples: [4] [6] [9] [11] [12] [15]

Square(float64) Shape

2D square with size in meter

examples: [6]

Universe() Shape

Entire space

XRange(float64, float64) Shape

Part of space between x1 (inclusive) and x2 (exclusive), in meter

examples: [4] [7]

YRange(float64, float64) Shape

Part of space between y1 (inclusive) and y2 (exclusive), in meter

ZRange(float64, float64) Shape

Part of space between z1 (inclusive) and z2 (exclusive), in meter

Material regions

Optionally, up to 256 material regions can be defined. Since each cell is made from one material, it is associated with exactly one region. So regions can not overlap. Each cell is assigned material region 0 by default. It's a good idea to output regions to verify whether each cell is assigned to the intended region. Each region can have its own material parameters, and we can output averages over each region. E.g.:

DefRegion(1, circle(1e-6))
DefRegion(0, circle(1e-6).Inverse()) // redundant
save(regions)
Msat.SetRegion(1, 800e6)
tableAdd(m.Region(1))    // add average m over region 1 to table

DefRegion(int, Shape)

Define a material region with given index (0-255) and shape

examples: [7] [12] [13]

DefRegionCell(int, int, int, int)

Set a material region (first argument) in one cell by the index of the cell (last three arguments)

regions

Outputs the region index for each cell

methods: Average( ) EvalTo( Slice ) GetCell( int int int ) Gpu( ) HostArray( ) HostList( ) LoadFile( string ) SetCell( int int int int )

examples: [7] [12]

Initial magnetization

The initial magnetization is set by assigning a Config to m, setting it in separate regions, or by loading a file directly.

m = uniform(1, 0, 0)
m.SetRegion(1, vortex(1, 1))
m.LoadFile("config.ovf")
m.SetInShape(circle(50e-9), uniform(0,0,1))

Reduced magnetization (unit length)

methods: Average( ) Buffer( ) Comp( int ) EvalTo( Slice ) GetCell( int int int ) LoadFile( string ) Quantity( ) Region( int ) Set( Config ) SetArray( Slice ) SetCell( int int int data.Vector ) SetInShape( Shape Config ) SetRegion( int Config )

examples: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]

Antivortex(int, int) Config

Antivortex magnetization with given circulation and core polarization

methods: Add( float64 Config ) RotZ( float64 ) Scale( float64 float64 float64 ) Transl( float64 float64 float64 )

BlochSkyrmion(int, int) Config

Bloch skyrmion magnetization with given chirality and core polarization

methods: Add( float64 Config ) RotZ( float64 ) Scale( float64 float64 float64 ) Transl( float64 float64 float64 )

examples: [5]

Conical(data.Vector, data.Vector, float64) Config

Conical state for given wave vector, cone direction, and cone angle

methods: Add( float64 Config ) RotZ( float64 ) Scale( float64 float64 float64 ) Transl( float64 float64 float64 )

Helical(data.Vector) Config

Helical state for given wave vector

methods: Add( float64 Config ) RotZ( float64 ) Scale( float64 float64 float64 ) Transl( float64 float64 float64 )

NeelSkyrmion(int, int) Config

Néél skyrmion magnetization with given charge and core polarization

methods: Add( float64 Config ) RotZ( float64 ) Scale( float64 float64 float64 ) Transl( float64 float64 float64 )

examples: [5]

RandomMag() Config

Random magnetization

methods: Add( float64 Config ) RotZ( float64 ) Scale( float64 float64 float64 ) Transl( float64 float64 float64 )

examples: [3] [5]

RandomMagSeed(int) Config

Random magnetization with given seed

methods: Add( float64 Config ) RotZ( float64 ) Scale( float64 float64 float64 ) Transl( float64 float64 float64 )

TwoDomain(float64, float64, float64, float64, float64, float64, float64, float64, float64) Config

Twodomain magnetization with with given magnetization in left domain, wall, and right domain

methods: Add( float64 Config ) RotZ( float64 ) Scale( float64 float64 float64 ) Transl( float64 float64 float64 )

examples: [5] [10] [11]

Uniform(float64, float64, float64) Config

Uniform magnetization in given direction

methods: Add( float64 Config ) RotZ( float64 ) Scale( float64 float64 float64 ) Transl( float64 float64 float64 )

examples: [1] [2] [5] [6] [7] [13] [14] [15]

Vortex(int, int) Config

Vortex magnetization with given circulation and core polarization

methods: Add( float64 Config ) RotZ( float64 ) Scale( float64 float64 float64 ) Transl( float64 float64 float64 )

examples: [5] [8] [9] [12]

VortexWall(float64, float64, int, int) Config

Vortex wall magnetization with given mx in left and right domain and core circulation and polarization

methods: Add( float64 Config ) RotZ( float64 ) Scale( float64 float64 float64 ) Transl( float64 float64 float64 )

examples: [5]

Material parameters

Assigning to a material parameter sets a value in all regions. E.g.:

Msat  = 800e3
AnisU = vector(1, 0, 0)

When regions are defined, they can also be set region-wise:

Msat.SetRegion(0, 800e3)
Msat.SetRegion(1, 540e3)

Material parameters can be functions of time as well. E.g.:

f := 500e6
Ku1 = 500 * sin(2*pi*f*t)

Aex

Exchange stiffness (J/m)

methods: Average( ) EvalTo( Slice ) GetRegion( int ) IsUniform( ) MSlice( ) Region( int ) Set( float64 ) SetRegion( int ScalarFunction ) SetRegionFuncGo( int func() float64 ) SetRegionValueGo( int float64 )

examples: [1] [2] [3] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]

alpha

Landau-Lifshitz damping constant

examples: [1] [6] [7] [8] [10] [11] [12] [14] [15]

anisC1

Cubic anisotropy direction #1

methods: Average( ) Comp( int ) EvalTo( Slice ) GetRegion( int ) IsUniform( ) MSlice( ) Region( int ) SetRegion( int VectorFunction ) SetRegionFn( int func() [3]float64 )

examples: [12]

anisC2

Cubic anisotorpy directon #2

methods: Average( ) Comp( int ) EvalTo( Slice ) GetRegion( int ) IsUniform( ) MSlice( ) Region( int ) SetRegion( int VectorFunction ) SetRegionFn( int func() [3]float64 )

examples: [12]

anisU

Uniaxial anisotropy direction

methods: Average( ) Comp( int ) EvalTo( Slice ) GetRegion( int ) IsUniform( ) MSlice( ) Region( int ) SetRegion( int VectorFunction ) SetRegionFn( int func() [3]float64 )

examples: [7] [10] [15]

First magneto-elastic coupling constant (J/m3)

Second magneto-elastic coupling constant (J/m3)

Dbulk

Bulk Dzyaloshinskii-Moriya strength (J/m2)

Dind

Interfacial Dzyaloshinskii-Moriya strength (J/m2)

EpsilonPrime

Slonczewski secondairy STT term ε'

examples: [14]

FreeLayerThickness

Slonczewski free layer thickness (if set to zero (default), then the thickness will be deduced from the mesh size) (m)

frozenspins

Defines spins that should be fixed

Kc1

1st order cubic anisotropy constant (J/m3)

examples: [12]

Kc2

2nd order cubic anisotropy constant (J/m3)

Kc3

3rd order cubic anisotropy constant (J/m3)

Ku1

1st order uniaxial anisotropy constant (J/m3)

examples: [7] [10] [15]

Ku2

2nd order uniaxial anisotropy constant (J/m3)

Lambda

Slonczewski Λ parameter

examples: [14]

Msat

Saturation magnetization (A/m)

examples: [1] [2] [3] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]

NoDemagSpins

Disable magnetostatic interaction per region (default=0, set to 1 to disable). E.g.: NoDemagSpins.SetRegion(5, 1) disables the magnetostatic interaction in region 5.

Pol

Electrical current polarization

examples: [5] [10] [11] [14]

Temp

Temperature (K)

Non-adiabaticity of spin-transfer-torque

examples: [10] [11] [12]

Excitation

Field or current excitations can be set in the same way as material parameters:

B_ext = vector(0.01, 1e-6*sin(2*pi*f*t), 0)
B_ext.SetRegion(1, vector(0, 0, 0.1))

Additionally, an arbitrary number of time- and space-dependent vector fields of the form g(x,y,z) * f(t) may be added. (E.g., to simulate the field of an antenna or an arbitrary current running through the magnet)

B_ext.Add(LoadFile("antenna.ovf"), sin(2*pi*f*t))
J.Add(LoadFile("current.ovf"), 1)

B_ext

Externally applied field (T)

methods: Add( Slice ScalarFunction ) AddGo( Slice func() float64 ) AddTo( Slice ) Average( ) Comp( int ) EvalTo( Slice ) IsUniform( ) MSlice( ) Region( int ) RemoveExtraTerms( ) Set( data.Vector ) SetRegion( int VectorFunction ) SetRegionFn( int func() [3]float64 )

examples: [1] [3] [15]

FixedLayer

Slonczewski fixed layer polarization

examples: [14]

Electrical current density (A/m2)

examples: [10] [11] [12] [13] [14] [15]

Spin currents

The effect of spin-polarized currents on the magnetization dynamics can be modelled in different ways. In Mumax3 you can use the Zhang-Li model or the Slonczewski model. For both models, a spin-polarized current field needs to be defined. This is done by setting the current density field J and the polarization Pol.

Zhang-Li model

When using the the Zhang-Li model, it is possible to set the non-adiabaticity through the material parameter xi:

J = vector(1e12, 0, 0)
Pol = 1
xi = 0.1

Slonczewski model

To use the Slonczewski model, you need to define the magnetization configuration of the fixed layer. This fixed layer can be placed above or below the sample. The Slonczewski parameter and the prefactor of the secondary spin transfer torque term of the Slonczewski model can be set through the material parameters Lambda and EpsilonPrime respectively:

DisableZhangLiTorque = true
J = vector(1e12, 0, 0)
Pol = 0.6
FixedLayer = vector(1,0,0)
FixedLayerPosition = FIXEDLAYER_TOP
EpsilonPrime = 0.02
Lambda = 1

DisableSlonczewskiTorque

Disables Slonczewski torque (default=false)

DisableZhangLiTorque

Disables Zhang-Li torque (default=false)

EpsilonPrime

Slonczewski secondairy STT term ε'

examples: [14]

FixedLayer

Slonczewski fixed layer polarization

examples: [14]

FIXEDLAYER_BOTTOM

FixedLayerPosition = FIXEDLAYER_BOTTOM instructs mumax3 that fixed layer is underneath of the free layer

FIXEDLAYER_TOP

FixedLayerPosition = FIXEDLAYER_TOP instructs mumax3 that fixed layer is on top of the free layer

FixedLayerPosition

Position of the fixed layer: FIXEDLAYER_TOP, FIXEDLAYER_BOTTOM (default=FIXEDLAYER_TOP)

FreeLayerThickness

Slonczewski free layer thickness (if set to zero (default), then the thickness will be deduced from the mesh size) (m)

Electrical current density (A/m2)

examples: [10] [11] [12] [13] [14] [15]

Lambda

Slonczewski Λ parameter

examples: [14]

Pol

Electrical current polarization

examples: [5] [10] [11] [14]

Non-adiabaticity of spin-transfer-torque

examples: [10] [11] [12]

Output quantities

The quantities listed below can be output.
Also, derived quantities can be produced: the quantity restricted to a certain region or a single component. E.g.:

m           // magnetization quantity
m.Comp(0)   // x-component
m.Region(1) // magnetization in region 1 (0 elsewhere)

Averaging behavior

.Average() yields the average over the entire simulation grid, except for m which is always averaged over the geometry.
For vector quantities, an average over the magnet geometry can still be obtained with the .Comp() method. E.g.:

B_demag.Average()          // Average vector over entire simulation grid
B_demag.Comp(1).Average()  // Average y-component over geometry
m.Average()                // Average magnetization over geometry

B_anis

Anisotropy field (T)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

B_custom

User-defined field (T)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

B_demag

Magnetostatic field (T)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

B_eff

Effective field (T)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

B_exch

Exchange field (T)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

B_mel

Magneto-elastic filed (T)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

B_therm

Thermal field (T)

methods: AddTo( Slice ) EvalTo( Slice )

DindCoupling

Average DMI coupling with neighbors (arb.)

methods: Average( ) EvalTo( Slice ) Region( int )

Time Step (s)

methods: Average( ) EvalTo( Slice ) Get( )

E_anis

total anisotropy energy (J)

methods: Average( ) EvalTo( Slice ) Get( )

E_custom

total energy of user-defined field (J)

methods: Average( ) EvalTo( Slice ) Get( )

E_demag

Magnetostatic energy (J)

methods: Average( ) EvalTo( Slice ) Get( )

E_exch

Total exchange energy (including the DMI energy) (J)

methods: Average( ) EvalTo( Slice ) Get( )

E_mel

Magneto-elastic energy (J)

methods: Average( ) EvalTo( Slice ) Get( )

E_therm

Thermal energy (J)

methods: Average( ) EvalTo( Slice ) Get( )

E_total

total energy (J)

methods: Average( ) EvalTo( Slice ) Get( )

examples: [13]

E_Zeeman

Zeeman energy (J)

methods: Average( ) EvalTo( Slice ) Get( )

Edens_anis

Anisotropy energy density (J/m3)

methods: Average( ) EvalTo( Slice ) Region( int )

Edens_custom

Energy density of user-defined field. (J/m3)

methods: Average( ) EvalTo( Slice ) Region( int )

Edens_demag

Magnetostatic energy density (J/m3)

methods: Average( ) EvalTo( Slice ) Region( int )

Edens_exch

Total exchange energy density (including the DMI energy density) (J/m3)

methods: Average( ) EvalTo( Slice ) Region( int )

Edens_mel

Magneto-elastic energy density (J/m3)

methods: Average( ) EvalTo( Slice ) Region( int )

Edens_therm

Thermal energy density (J/m3)

methods: Average( ) EvalTo( Slice ) Region( int )

Edens_total

Total energy density (J/m3)

methods: Average( ) EvalTo( Slice ) Region( int )

Edens_Zeeman

Zeeman energy density (J/m3)

methods: Average( ) EvalTo( Slice ) Region( int )

ExchCoupling

Average exchange coupling with neighbors (arb.)

methods: Average( ) EvalTo( Slice ) Region( int )

examples: [12]

F_mel

Magneto-elastic force density (N/m3)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

geom

Cell fill fraction (0..1)

methods: Average( ) EvalTo( Slice ) Gpu( )

examples: [4] [6] [7] [8] [9] [11] [12] [14]

LastErr

Error of last step

methods: Average( ) EvalTo( Slice ) Get( )

LLtorque

Landau-Lifshitz torque/γ0 (T)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

Reduced magnetization (unit length)

examples: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]

m_full

Unnormalized magnetization (A/m)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

MaxAngle

maximum angle between neighboring spins (rad)

methods: Average( ) EvalTo( Slice ) Get( )

maxTorque

Maximum torque/γ0, over all cells (T)

methods: Average( ) EvalTo( Slice ) Get( )

MFM

MFM image (arb.)

methods: Average( ) EvalTo( Slice ) Region( int )

examples: [9]

NEval

Total number of torque evaluations

methods: Average( ) EvalTo( Slice ) Get( )

PeakErr

Overall maxium error per step

methods: Average( ) EvalTo( Slice ) Get( )

spinAngle

Angle between neighboring spins (rad)

methods: Average( ) EvalTo( Slice ) Region( int )

STTorque

Spin-transfer torque/γ0 (T)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

torque

Total torque/γ0 (T)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

Slicing and dicing output

To save storage space, it's possible to save only the part of the output we're interested in. This works on all output quantities (not only m).

save(m)                         // save full magnetization
save(m.Comp(0))                 // save only x-component
save(CropLayer(m, 13))          // save only layer 13
save(CropLayer(m.Comp(0), 13))  // save only x-component of layer 13

Or even:

mx   := m.Comp(0)
mx13 := CropLayer(mx, 13) 
save(mx13)
tableAdd(mx13)

Crop(Quantity, int, int, int, int, int, int) *cropped

Crops a quantity to cell ranges [x1,x2[, [y1,y2[, [z1,z2[

methods: Average( ) EvalTo( Slice )

examples: [8]

CropLayer(Quantity, int) *cropped

Crops a quantity to a single layer

methods: Average( ) EvalTo( Slice )

CropRegion(Quantity, int) *cropped

Crops a quantity to a region

methods: Average( ) EvalTo( Slice )

CropX(Quantity, int, int) *cropped

Crops a quantity to cell ranges [x1,x2[

methods: Average( ) EvalTo( Slice )

CropY(Quantity, int, int) *cropped

Crops a quantity to cell ranges [y1,y2[

methods: Average( ) EvalTo( Slice )

examples: [8]

CropZ(Quantity, int, int) *cropped

Crops a quantity to cell ranges [z1,z2[

methods: Average( ) EvalTo( Slice )

Scheduling output

All input and output quantities (as described above) can be saved in a space-dependent way (.ovf file), or as spatial averages (table output). The data table (table.txt) contains by default the time and average magnetization. More columns can be added with TableAdd().

save(B_ext)

tableadd(B_ext)
tablesave()

Optionally, the output/averaging can be done over a single region:

save(m.Region(1))
TableAdd(m.Region(1))

User-defined variables can be added to the table with TableAddVar().

myField := 0.42
TableAddVar(myField, "B_extra", "T")
myField = ...

AutoSave(Quantity, float64)

Auto save space-dependent quantity every period (s).

examples: [1] [10] [11] [14] [15]

AutoSnapshot(Quantity, float64)

Auto save image of quantity every period (s).

DUMP

OutputFormat = DUMP sets text DUMP output

FilenameFormat

printf formatting string for output filenames.

Flush()

Flush all pending output to disk.

Fprintln(string, ...interface {})

Print to file

OutputFormat

Format for data files: OVF1_TEXT, OVF1_BINARY, OVF2_TEXT or OVF2_BINARY

OVF1_BINARY

OutputFormat = OVF1_BINARY sets binary OVF1 output

OVF1_TEXT

OutputFormat = OVF1_TEXT sets text OVF1 output

OVF2_BINARY

OutputFormat = OVF2_BINARY sets binary OVF2 output

OVF2_TEXT

OutputFormat = OVF2_TEXT sets text OVF2 output

Print(...interface {})

Print to standard output

examples: [2]

Save(Quantity)

Save space-dependent quantity once, with auto filename

examples: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]

SaveAs(Quantity, string)

Save space-dependent quantity with custom filename

examples: [4] [5] [7] [9]

Snapshot(Quantity)

Save image of quantity

SnapshotAs(Quantity, string)

Save image of quantity with custom filename

SnapshotFormat

Image format for snapshots: jpg, png or gif.

sprint(...interface {}) string

Print all arguments to string with automatic formatting

sprintf(string, ...interface {}) string

Print to string with C-style formatting.

TableAdd(Quantity)

Add quantity as a column to the data table.

examples: [3] [11] [13]

TableAddVar(ScalarFunction, string, string)

Add user-defined variable + name + unit to data table.

TableAutoSave(float64)

Auto-save the data table every period (s). Zero disables save.

examples: [1] [11] [14]

TablePrint(...interface {})

Print anyting in the data table

TableSave()

Save the data table right now (appends one line).

examples: [3] [13]

Running

Run(time) runs the simulation for a given time in seconds, using sensible error settings.

Run(1e-9)

More fine-grained control is provided by RunWhile(condition), which runs as long as an arbitrary condition is met. E.g.:

mx := m.comp(0)
RunWhile(mx.average() < 0)   // search for switching field during reversal

Optionally, the solver accuracy may be fine-tuned. E.g.:

MaxDt = 1e-12
MinDt = 1e-15
MaxErr = 1e-6

Optionally, a different solver may be chosen (at any point) with SetSolver(int). Currently available solver types:

6: RK56 (Fehlberg) solver. This is the highest order solver available, but which is typically not faster than the RK45 solver.
5: RK45 (Dormand-Prince) solver (the default). An accurate solver, very fast for magnetization dynamics at the cost of some memory usage.
4: Classical 4th-order Runge-Kutta method. Intended for simulations where a fixed, relatively large time step is desired.
3: RK23 (Bogacki-Shampine) solver. A robust and reasonably fast solver with low memory requirements. Typically outperforms RK45 when relaxing the magnetization with little dynamics, so it used internally by Relax().
2: Adaptive Heun solver. Robust and uses very little memory but takes smaller time steps than the higher-order solvers. Also suited when a fixed, relatively small time step is desired.
1: Euler solver (requires FixDt = ..., ignores other settings). Only useful in exceptional situations or for debugging.

E.g.:

SetSolver(2) // Heun
FixDt = 1e-15

Relax

Relax() tries to evolve the magnetization as closely as possible to the minimum energy state. This function assumes all excitations have been turned off (temperature, electrical current, time-dependent magnetic fields). During relax precession is disabled and the time t does not increase. There is no need to set high damping.

In general it is difficult to be sure the minimum energy state has been truly reached. Hence, relax may occasionally return after the energy has reached a local minimum, a saddle point, or a rather flat valley in the energy landscape.

Minimize

Minimize() is like Relax, but uses the conjugate gradient method to find the energy minimum. It is usually much faster than Relax, but is a bit less robust against divergence. E.g., a random starting configuration can be Relaxed, but may fail with Minimize. Minimize is very well suited for hysteresis calculations, where we are never far away from the ground state.

Minimize()

Use steepest conjugate gradient method to minimize the total energy

examples: [3] [6]

Relax()

Try to minimize the total energy

examples: [1] [2] [3] [9] [10] [11]

Run(float64)

Run the simulation for a time in seconds

examples: [1] [7] [10] [11] [12] [14] [15]

RunWhile(func() bool)

Run while condition function is true

Steps(int)

Run the simulation for a number of time steps

Time Step (s)

methods: Average( ) EvalTo( Slice ) Get( )

FixDt

Set a fixed time step, 0 disables fixed step (which is the default)

Headroom

Solver headroom (default = 0.8)

LastErr

Error of last step

methods: Average( ) EvalTo( Slice ) Get( )

MaxDt

Maximum time step the solver can take (s)

MaxErr

Maximum error per step the solver can tolerate (default = 1e-5)

MinDt

Minimum time step the solver can take (s)

MinimizerSamples

Number of max dM to collect for Minimize convergence check.

MinimizerStop

Stopping max dM for Minimize

examples: [3]

NEval

Total number of torque evaluations

methods: Average( ) EvalTo( Slice ) Get( )

PeakErr

Overall maxium error per step

methods: Average( ) EvalTo( Slice ) Get( )

RelaxTorqueThreshold

MaxTorque threshold for relax(). If set to -1 (default), relax() will stop when the average torque is steady or increasing.

step

Total number of time steps taken

examples: [3] [10]

Total simulated time (s)

examples: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]

SetSolver(int)

Set solver type. 1:Euler, 2:Heun, 3:Bogaki-Shampine, 4: Runge-Kutta (RK4), 5: Dormand-Prince, 6: Fehlberg, -1: Backward Euler

Moving simulation window

mumax³ can automatically shift the magnetization so that the simulation "window" stays centered on a region of interest. Shifting is done to keep a freely chosen magnetization component nearly zero. E.g.

ext_centerwall(0)
ext_rmSurfaceCharge(0, -1, 1)
TableAdd(TotalShift)

will try to keep mx (component 0, counting from 0) close to zero. If desired, one can override which "new" magnetization is inserted from the sides by setting ShiftMagL and ShiftMagR, though the default behaviour is usually OK.

Shift(int)

Shifts the simulation by +1/-1 cells along X

examples: [15]

ShiftGeom

Whether Shift() acts on geometry

ShiftM

Whether Shift() acts on magnetization

examples: [15]

ShiftMagD

Upon shift, insert this magnetization from the bottom

methods: Add( data.Vector ) Cross( data.Vector ) Div( float64 ) Dot( data.Vector ) Len( ) MAdd( float64 data.Vector ) Mul( float64 ) Sub( data.Vector ) X( ) Y( ) Z( )

ShiftMagL

Upon shift, insert this magnetization from the left

methods: Add( data.Vector ) Cross( data.Vector ) Div( float64 ) Dot( data.Vector ) Len( ) MAdd( float64 data.Vector ) Mul( float64 ) Sub( data.Vector ) X( ) Y( ) Z( )

ShiftMagR

Upon shift, insert this magnetization from the right

methods: Add( data.Vector ) Cross( data.Vector ) Div( float64 ) Dot( data.Vector ) Len( ) MAdd( float64 data.Vector ) Mul( float64 ) Sub( data.Vector ) X( ) Y( ) Z( )

examples: [15]

ShiftMagU

Upon shift, insert this magnetization from the top

methods: Add( data.Vector ) Cross( data.Vector ) Div( float64 ) Dot( data.Vector ) Len( ) MAdd( float64 data.Vector ) Mul( float64 ) Sub( data.Vector ) X( ) Y( ) Z( )

ShiftRegions

Whether Shift() acts on regions

TotalShift

Amount by which the simulation has been shifted (m).

Custom quantities

Using existing quantities, it is possible to define new custom quantities. E.g.: instead of using the pre-defined ext_topologicalchargedensity quantity, it is possible to define this quantity yourselves inside an input script:

cs := 1e-9
setcellsize(cs,cs,cs)
setgridsize(64,64,1)

// Use central finite differences to approximate the spatial derivatives of m
mL := Shifted(m,-1,0,0) // shift left
mR := Shifted(m,1,0,0)  // shift right
mD := Shifted(m,0,-1,0) // shift up
mU := Shifted(m,0,1,0)  // shift down
dmdx := Mul( Const(1/(2*cs)), Madd(mR,mL,1,-1) )
dmdy := Mul( Const(1/(2*cs)), Madd(mU,mD,1,-1) ) 

// Define the topological charge density
chargeDensity := Mul( Const(1/(4*pi)), Dot(m, Cross(dmdx,dmdy)))

// Save the topological charge density of a skyrmion
m = neelskyrmion(1,-1)
saveas(chargeDensity, "chargeDensity.ovf")

Add(Quantity, Quantity) Quantity

Add two quantities

methods: EvalTo( )

examples: [3] [4] [5] [11] [13] [15]

Const(float64) Quantity

Constant, uniform number

methods: EvalTo( )

ConstVector(float64, float64, float64) Quantity

Constant, uniform vector

methods: EvalTo( )

Cross(Quantity, Quantity) Quantity

Cross product of two vector quantities

methods: EvalTo( )

examples: [12]

Div(Quantity, Quantity) Quantity

Point-wise division of two quantities

methods: EvalTo( )

Dot(Quantity, Quantity) Quantity

Dot product of two vector quantities

methods: EvalTo( )

Madd(Quantity, Quantity, float64, float64) *mAddition

Weighted addition: Madd(Q1,Q2,c1,c2) = c1*Q1 + c2*Q2

methods: EvalTo( Slice )

Masked(Quantity, Shape) Quantity

Mask quantity with shape

methods: EvalTo( )

Mul(Quantity, Quantity) Quantity

Point-wise product of two quantities

methods: EvalTo( )

examples: [10] [11]

MulMV(Quantity, Quantity, Quantity, Quantity) Quantity

Matrix-Vector product: MulMV(AX, AY, AZ, m) = (AX·m, AY·m, AZ·m). The arguments Ax, Ay, Az and m are quantities with 3 componets.

methods: EvalTo( )

Shifted(Quantity, int, int, int) Quantity

Shifted quantity

methods: EvalTo( )

Custom effective field terms

It is possible to define additional effective field terms by promoting a custom quantity to an effective field term. The corresponding energy density term can also be added by promoting a custom quantity. E.g.: instead of using the existing anistropy field in mumax³, you could define the uniaxial anisotropy field (and the corresponding energy density) yourselves:


Ms := 1100e3
K  := 0.5e6
u  := ConstVector(1, 0, 0)
anisField := Mul( Const(2*K/Ms)  , Mul( Dot(u, m), u))
anisEdens := Mul( Const(-0.5*Ms) , Dot( anisField, m))

AddFieldTerm(anisField) // promote anisField to an effective field term
AddEdensTerm(anisEdens) // promote anisEdens to an energy density term

tableAdd(E_custom)  // Add a column with the energy related to the custom field

AddEdensTerm(Quantity)

Add an expression to Edens.

AddFieldTerm(Quantity)

Add an expression to B_eff.

B_custom

User-defined field (T)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

E_custom

total energy of user-defined field (J)

methods: Average( ) EvalTo( Slice ) Get( )

Edens_custom

Energy density of user-defined field. (J/m3)

methods: Average( ) EvalTo( Slice ) Region( int )

RemoveCustomFields()

Removes all custom fields again

abs(float64) float64

Abs returns the absolute value of x.

acos(float64) float64

Acos returns the arccosine, in radians, of x.

acosh(float64) float64

Acosh returns the inverse hyperbolic cosine of x.

Add(Quantity, Quantity) Quantity

Add two quantities

methods: EvalTo( )

examples: [3] [4] [5] [11] [13] [15]

AddEdensTerm(Quantity)

Add an expression to Edens.

AddFieldTerm(Quantity)

Add an expression to B_eff.

Aex

Exchange stiffness (J/m)

examples: [1] [2] [3] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]

alpha

Landau-Lifshitz damping constant

examples: [1] [6] [7] [8] [10] [11] [12] [14] [15]

anisC1

Cubic anisotropy direction #1

methods: Average( ) Comp( int ) EvalTo( Slice ) GetRegion( int ) IsUniform( ) MSlice( ) Region( int ) SetRegion( int VectorFunction ) SetRegionFn( int func() [3]float64 )

examples: [12]

anisC2

Cubic anisotorpy directon #2

methods: Average( ) Comp( int ) EvalTo( Slice ) GetRegion( int ) IsUniform( ) MSlice( ) Region( int ) SetRegion( int VectorFunction ) SetRegionFn( int func() [3]float64 )

examples: [12]

anisU

Uniaxial anisotropy direction

methods: Average( ) Comp( int ) EvalTo( Slice ) GetRegion( int ) IsUniform( ) MSlice( ) Region( int ) SetRegion( int VectorFunction ) SetRegionFn( int func() [3]float64 )

examples: [7] [10] [15]

Antivortex(int, int) Config

Antivortex magnetization with given circulation and core polarization

methods: Add( float64 Config ) RotZ( float64 ) Scale( float64 float64 float64 ) Transl( float64 float64 float64 )

asin(float64) float64

Asin returns the arcsine, in radians, of x.

asinh(float64) float64

Asinh returns the inverse hyperbolic sine of x.

atan(float64) float64

Atan returns the arctangent, in radians, of x.

atan2(float64, float64) float64

Atan2 returns the arc tangent of y/x, using the signs of the two to determine the quadrant of the return value.

atanh(float64) float64

Atanh returns the inverse hyperbolic tangent of x.

AutoSave(Quantity, float64)

Auto save space-dependent quantity every period (s).

examples: [1] [10] [11] [14] [15]

AutoSnapshot(Quantity, float64)

Auto save image of quantity every period (s).

First magneto-elastic coupling constant (J/m3)

Second magneto-elastic coupling constant (J/m3)

B_anis

Anisotropy field (T)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

B_custom

User-defined field (T)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

B_demag

Magnetostatic field (T)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

B_eff

Effective field (T)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

B_exch

Exchange field (T)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

B_ext

Externally applied field (T)

examples: [1] [3] [15]

B_mel

Magneto-elastic filed (T)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

B_therm

Thermal field (T)

methods: AddTo( Slice ) EvalTo( Slice )

BlochSkyrmion(int, int) Config

Bloch skyrmion magnetization with given chirality and core polarization

methods: Add( float64 Config ) RotZ( float64 ) Scale( float64 float64 float64 ) Transl( float64 float64 float64 )

examples: [5]

cbrt(float64) float64

Cbrt returns the cube root of x.

ceil(float64) float64

Ceil returns the least integer value greater than or equal to x.

Cell(int, int, int) Shape

Single cell with given integer index (i, j, k)

examples: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]

Circle(float64) Shape

2D Circle with diameter in meter

examples: [4] [6] [7] [8] [12]

Cone(float64, float64) Shape

3D Cone with diameter and height in meter. The top of the cone points in the +z direction.

Conical(data.Vector, data.Vector, float64) Config

Conical state for given wave vector, cone direction, and cone angle

methods: Add( float64 Config ) RotZ( float64 ) Scale( float64 float64 float64 ) Transl( float64 float64 float64 )

Const(float64) Quantity

Constant, uniform number

methods: EvalTo( )

ConstVector(float64, float64, float64) Quantity

Constant, uniform vector

methods: EvalTo( )

cos(float64) float64

Cos returns the cosine of the radian argument x.

examples: [6] [13] [14]

cosh(float64) float64

Cosh returns the hyperbolic cosine of x.

Crop(Quantity, int, int, int, int, int, int) *cropped

Crops a quantity to cell ranges [x1,x2[, [y1,y2[, [z1,z2[

methods: Average( ) EvalTo( Slice )

examples: [8]

CropLayer(Quantity, int) *cropped

Crops a quantity to a single layer

methods: Average( ) EvalTo( Slice )

CropRegion(Quantity, int) *cropped

Crops a quantity to a region

methods: Average( ) EvalTo( Slice )

CropX(Quantity, int, int) *cropped

Crops a quantity to cell ranges [x1,x2[

methods: Average( ) EvalTo( Slice )

CropY(Quantity, int, int) *cropped

Crops a quantity to cell ranges [y1,y2[

methods: Average( ) EvalTo( Slice )

examples: [8]

CropZ(Quantity, int, int) *cropped

Crops a quantity to cell ranges [z1,z2[

methods: Average( ) EvalTo( Slice )

Cross(Quantity, Quantity) Quantity

Cross product of two vector quantities

methods: EvalTo( )

examples: [12]

Cuboid(float64, float64, float64) Shape

Cuboid with sides in meter

examples: [4]

Cylinder(float64, float64) Shape

3D Cylinder with diameter and height in meter

examples: [4] [5] [6]

Dbulk

Bulk Dzyaloshinskii-Moriya strength (J/m2)

DefRegion(int, Shape)

Define a material region with given index (0-255) and shape

examples: [7] [12] [13]

DefRegionCell(int, int, int, int)

Set a material region (first argument) in one cell by the index of the cell (last three arguments)

DemagAccuracy

Controls accuracy of demag kernel

Dind

Interfacial Dzyaloshinskii-Moriya strength (J/m2)

DindCoupling

Average DMI coupling with neighbors (arb.)

methods: Average( ) EvalTo( Slice ) Region( int )

DisableSlonczewskiTorque

Disables Slonczewski torque (default=false)

DisableZhangLiTorque

Disables Zhang-Li torque (default=false)

Div(Quantity, Quantity) Quantity

Point-wise division of two quantities

methods: EvalTo( )

DoPrecess

Enables LL precession (default=true)

Dot(Quantity, Quantity) Quantity

Dot product of two vector quantities

methods: EvalTo( )

Time Step (s)

methods: Average( ) EvalTo( Slice ) Get( )

DUMP

OutputFormat = DUMP sets text DUMP output

E_anis

total anisotropy energy (J)

methods: Average( ) EvalTo( Slice ) Get( )

E_custom

total energy of user-defined field (J)

methods: Average( ) EvalTo( Slice ) Get( )

E_demag

Magnetostatic energy (J)

methods: Average( ) EvalTo( Slice ) Get( )

E_exch

Total exchange energy (including the DMI energy) (J)

methods: Average( ) EvalTo( Slice ) Get( )

E_mel

Magneto-elastic energy (J)

methods: Average( ) EvalTo( Slice ) Get( )

E_therm

Thermal energy (J)

methods: Average( ) EvalTo( Slice ) Get( )

E_total

total energy (J)

methods: Average( ) EvalTo( Slice ) Get( )

examples: [13]

E_Zeeman

Zeeman energy (J)

methods: Average( ) EvalTo( Slice ) Get( )

Edens_anis

Anisotropy energy density (J/m3)

methods: Average( ) EvalTo( Slice ) Region( int )

Edens_custom

Energy density of user-defined field. (J/m3)

methods: Average( ) EvalTo( Slice ) Region( int )

Edens_demag

Magnetostatic energy density (J/m3)

methods: Average( ) EvalTo( Slice ) Region( int )

Edens_exch

Total exchange energy density (including the DMI energy density) (J/m3)

methods: Average( ) EvalTo( Slice ) Region( int )

Edens_mel

Magneto-elastic energy density (J/m3)

methods: Average( ) EvalTo( Slice ) Region( int )

Edens_therm

Thermal energy density (J/m3)

methods: Average( ) EvalTo( Slice ) Region( int )

Edens_total

Total energy density (J/m3)

methods: Average( ) EvalTo( Slice ) Region( int )

Edens_Zeeman

Zeeman energy density (J/m3)

methods: Average( ) EvalTo( Slice ) Region( int )

EdgeSmooth

Geometry edge smoothing with edgeSmooth^3 samples per cell, 0=staircase, ~8=very smooth

examples: [4]

Ellipse(float64, float64) Shape

2D Ellipse with axes in meter

examples: [14]

Ellipsoid(float64, float64, float64) Shape

3D Ellipsoid with axes in meter

examples: [4]

EnableDemag

Enables/disables demag (default=true)

EpsilonPrime

Slonczewski secondairy STT term ε'

examples: [14]

erf(float64) float64

Erf returns the error function of x.

erfc(float64) float64

Erfc returns the complementary error function of x.

ExchCoupling

Average exchange coupling with neighbors (arb.)

methods: Average( ) EvalTo( Slice ) Region( int )

examples: [12]

Exit()

Exit from the program

exp(float64) float64

Exp returns e**x, the base-e exponential of x.

examples: [15]

exp2(float64) float64

Exp2 returns 2**x, the base-2 exponential of x.

Expect(string, float64, float64, float64)

Used for automated tests: checks if a value is close enough to the expected value

ExpectV(string, data.Vector, data.Vector, float64)

Used for automated tests: checks if a vector is close enough to the expected value

expm1(float64) float64

Expm1 returns e**x - 1, the base-e exponential of x minus 1. It is more accurate than Exp(x) - 1 when x is near zero.

ext_bubbledist

Bubble traveled distance (m)

methods: Average( ) EvalTo( Slice ) Get( )

ext_BubbleMz

Center magnetization 1.0 or -1.0 (default = 1.0)

ext_bubblepos

Bubble core position (m)

methods: Average( ) EvalTo( Slice ) Get( )

ext_bubblespeed

Bubble velocity (m/s)

methods: Average( ) EvalTo( Slice ) Get( )

ext_centerBubble()

centerBubble shifts m after each step to keep the bubble position close to the center of the window

ext_centerWall(int)

centerWall(c) shifts m after each step to keep m_c close to zero

examples: [10] [11]

ext_corepos

Vortex core position (x,y) + polarization (z) (m)

methods: Average( ) EvalTo( Slice ) Get( )

ext_dwpos

Position of the simulation window while following a domain wall (m)

methods: Average( ) EvalTo( Slice ) Get( )

examples: [11]

ext_dwspeed

Speed of the simulation window while following a domain wall (m/s)

methods: Average( ) EvalTo( Slice ) Get( )

ext_dwtilt

PMA domain wall tilt (rad)

methods: Average( ) EvalTo( Slice ) Get( )

ext_dwxpos

Position of the simulation window while following a domain wall (m)

methods: Average( ) EvalTo( Slice ) Get( )

ext_EnableUnsafe()

Deprecated. Only here to ensure maximal backwards compatibility with mumax3.9c.

ext_InterDind(int, int, float64)

Sets Dind coupling between two regions.

ext_InterExchange(int, int, float64)

Sets exchange coupling between two regions.

ext_make3dgrains(float64, int, int, Shape, int)

3D Voronoi tesselation over shape (grain size, starting region number, num regions, shape, seed)

ext_makegrains(float64, int, int)

Voronoi tesselation (grain size, num regions)

examples: [12] [15]

ext_phi

Azimuthal angle (rad)

methods: Average( ) EvalTo( Slice ) Region( int )

ext_rmSurfaceCharge(int, float64, float64)

Compensate magnetic charges on the left and right sides of an in-plane magnetized wire. Arguments: region, mx on left and right side, resp.

examples: [11]

ext_ScaleDind(int, int, float64)

Re-scales Dind coupling between two regions.

ext_ScaleExchange(int, int, float64)

Re-scales exchange coupling between two regions.

examples: [12] [13] [15]

ext_theta

Polar angle (rad)

methods: Average( ) EvalTo( Slice ) Region( int )

ext_topologicalcharge

2D topological charge

methods: Average( ) EvalTo( Slice ) Get( )

ext_topologicalchargedensity

2D topological charge density m·(∂m/∂x ✕ ∂m/∂y) (1/m2)

methods: Average( ) EvalTo( Slice ) Region( int )

ext_topologicalchargedensitylattice

2D topological charge density according to Berg and Lüscher (1/m2)

methods: Average( ) EvalTo( Slice ) Region( int )

ext_topologicalchargelattice

2D topological charge according to Berg and Lüscher

methods: Average( ) EvalTo( Slice ) Get( )

exx

exx component of the strain tensor

methods: Add( Slice ScalarFunction ) AddGo( Slice func() float64 ) AddTo( Slice ) Average( ) Comp( int ) EvalTo( Slice ) IsUniform( ) MSlice( ) Region( int ) RemoveExtraTerms( ) Set( float64 ) SetRegion( int ScalarFunction ) SetRegionFn( int func() [3]float64 )

exy

exy component of the strain tensor

methods: Add( Slice ScalarFunction ) AddGo( Slice func() float64 ) AddTo( Slice ) Average( ) Comp( int ) EvalTo( Slice ) IsUniform( ) MSlice( ) Region( int ) RemoveExtraTerms( ) Set( float64 ) SetRegion( int ScalarFunction ) SetRegionFn( int func() [3]float64 )

exz

exz component of the strain tensor

methods: Add( Slice ScalarFunction ) AddGo( Slice func() float64 ) AddTo( Slice ) Average( ) Comp( int ) EvalTo( Slice ) IsUniform( ) MSlice( ) Region( int ) RemoveExtraTerms( ) Set( float64 ) SetRegion( int ScalarFunction ) SetRegionFn( int func() [3]float64 )

eyy

eyy component of the strain tensor

methods: Add( Slice ScalarFunction ) AddGo( Slice func() float64 ) AddTo( Slice ) Average( ) Comp( int ) EvalTo( Slice ) IsUniform( ) MSlice( ) Region( int ) RemoveExtraTerms( ) Set( float64 ) SetRegion( int ScalarFunction ) SetRegionFn( int func() [3]float64 )

eyz

eyz component of the strain tensor

methods: Add( Slice ScalarFunction ) AddGo( Slice func() float64 ) AddTo( Slice ) Average( ) Comp( int ) EvalTo( Slice ) IsUniform( ) MSlice( ) Region( int ) RemoveExtraTerms( ) Set( float64 ) SetRegion( int ScalarFunction ) SetRegionFn( int func() [3]float64 )

ezz

ezz component of the strain tensor

methods: Add( Slice ScalarFunction ) AddGo( Slice func() float64 ) AddTo( Slice ) Average( ) Comp( int ) EvalTo( Slice ) IsUniform( ) MSlice( ) Region( int ) RemoveExtraTerms( ) Set( float64 ) SetRegion( int ScalarFunction ) SetRegionFn( int func() [3]float64 )

F_mel

Magneto-elastic force density (N/m3)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

false

FilenameFormat

printf formatting string for output filenames.

FixDt

Set a fixed time step, 0 disables fixed step (which is the default)

FixedLayer

Slonczewski fixed layer polarization

examples: [14]

FIXEDLAYER_BOTTOM

FixedLayerPosition = FIXEDLAYER_BOTTOM instructs mumax3 that fixed layer is underneath of the free layer

FIXEDLAYER_TOP

FixedLayerPosition = FIXEDLAYER_TOP instructs mumax3 that fixed layer is on top of the free layer

FixedLayerPosition

Position of the fixed layer: FIXEDLAYER_TOP, FIXEDLAYER_BOTTOM (default=FIXEDLAYER_TOP)

floor(float64) float64

Floor returns the greatest integer value less than or equal to x.

Flush()

Flush all pending output to disk.

Fprintln(string, ...interface {})

Print to file

FreeLayerThickness

Slonczewski free layer thickness (if set to zero (default), then the thickness will be deduced from the mesh size) (m)

frozenspins

Defines spins that should be fixed

gamma(float64) float64

Gamma returns the Gamma function of x.

GammaLL

Gyromagnetic ratio in rad/Ts

geom

Cell fill fraction (0..1)

methods: Average( ) EvalTo( Slice ) Gpu( )

examples: [4] [6] [7] [8] [9] [11] [12] [14]

GrainRoughness(float64, float64, float64, int) Shape

Headroom

Solver headroom (default = 0.8)

heaviside(float64) float64

Returns 1 if x>0, 0 if x<0, and 0.5 if x==0

Helical(data.Vector) Config

Helical state for given wave vector

methods: Add( float64 Config ) RotZ( float64 ) Scale( float64 float64 float64 ) Transl( float64 float64 float64 )

hypot(float64, float64) float64

Hypot returns Sqrt(p*p + q*q), taking care to avoid unnecessary overflow and underflow.

ilogb(float64) int

Ilogb returns the binary exponent of x as an integer.

examples: [2]

ImageShape(string) Shape

Use black/white image as shape

examples: [4]

Index2Coord(int, int, int) data.Vector

Convert cell index to x,y,z coordinate in meter

methods: Add( data.Vector ) Cross( data.Vector ) Div( float64 ) Dot( data.Vector ) Len( ) MAdd( float64 data.Vector ) Mul( float64 ) Sub( data.Vector ) X( ) Y( ) Z( )

examples: [15]

inf

Inf returns positive infinity if sign >= 0, negative infinity if sign < 0.

examples: [4] [7] [11]

isInf(float64, int) bool

IsInf reports whether f is an infinity, according to sign. If sign > 0, IsInf reports whether f is positive infinity. If sign < 0, IsInf reports

isNaN(float64) bool

IsNaN reports whether f is an IEEE 754 “not-a-number” value.

Electrical current density (A/m2)

examples: [10] [11] [12] [13] [14] [15]

j0(float64) float64

J0 returns the order-zero Bessel function of the first kind.

j1(float64) float64

J1 returns the order-one Bessel function of the first kind.

jn(int, float64) float64

Jn returns the order-n Bessel function of the first kind.

Kc1

1st order cubic anisotropy constant (J/m3)

examples: [12]

Kc2

2nd order cubic anisotropy constant (J/m3)

Kc3

3rd order cubic anisotropy constant (J/m3)

Ku1

1st order uniaxial anisotropy constant (J/m3)

examples: [7] [10] [15]

Ku2

2nd order uniaxial anisotropy constant (J/m3)

Lambda

Slonczewski Λ parameter

examples: [14]

LastErr

Error of last step

methods: Average( ) EvalTo( Slice ) Get( )

Layer(int) Shape

Single layer (along z), by integer index starting from 0

examples: [4] [13] [14]

Layers(int, int) Shape

Part of space between cell layer1 (inclusive) and layer2 (exclusive), in integer indices

examples: [4]

ldexp(float64, int) float64

Ldexp is the inverse of Frexp. It returns frac × 2**exp.

LLtorque

Landau-Lifshitz torque/γ0 (T)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

LoadFile(string) Slice

Load a data file (ovf or dump)

methods: CPUAccess( ) Comp( int ) DevPtr( int ) Disable( ) Free( ) GPUAccess( ) Get( int int int int ) Host( ) HostCopy( ) Index( int int int ) IsNil( ) Len( ) MemType( ) Scalars( ) Set( int int int int float64 ) SetScalar( int int int float64 ) SetVector( int int int data.Vector ) Size( ) Tensors( ) Vectors( )

examples: [5]

log(float64) float64

Log returns the natural logarithm of x.

examples: [2] [4]

log10(float64) float64

Log10 returns the decimal logarithm of x. The special cases are the same as for Log.

log1p(float64) float64

Log1p returns the natural logarithm of 1 plus its argument x. It is more accurate than Log(1 + x) when x is near zero.

log2(float64) float64

Log2 returns the binary logarithm of x. The special cases are the same as for Log.

logb(float64) float64

Logb returns the binary exponent of x.

examples: [2]

Reduced magnetization (unit length)

examples: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]

m_full

Unnormalized magnetization (A/m)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

Madd(Quantity, Quantity, float64, float64) *mAddition

Weighted addition: Madd(Q1,Q2,c1,c2) = c1*Q1 + c2*Q2

methods: EvalTo( Slice )

Masked(Quantity, Shape) Quantity

Mask quantity with shape

methods: EvalTo( )

max(float64, float64) float64

Max returns the larger of x or y.

examples: [3] [12]

MaxAngle

maximum angle between neighboring spins (rad)

methods: Average( ) EvalTo( Slice ) Get( )

MaxDt

Maximum time step the solver can take (s)

MaxErr

Maximum error per step the solver can tolerate (default = 1e-5)

maxTorque

Maximum torque/γ0, over all cells (T)

methods: Average( ) EvalTo( Slice ) Get( )

MFM

MFM image (arb.)

methods: Average( ) EvalTo( Slice ) Region( int )

examples: [9]

MFMDipole

Height of vertically magnetized part of MFM tip

MFMLift

MFM lift height

examples: [9]

min(float64, float64) float64

Min returns the smaller of x or y.

examples: [3] [6]

MinDt

Minimum time step the solver can take (s)

Minimize()

Use steepest conjugate gradient method to minimize the total energy

examples: [3] [6]

MinimizerSamples

Number of max dM to collect for Minimize convergence check.

MinimizerStop

Stopping max dM for Minimize

examples: [3]

mod(float64, float64) float64

Mod returns the floating-point remainder of x/y. The magnitude of the result is less than y and its sign agrees with that of x.

Msat

Saturation magnetization (A/m)

examples: [1] [2] [3] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]

Mu0

Vacuum permeability (Tm/A)

examples: [2]

Mul(Quantity, Quantity) Quantity

Point-wise product of two quantities

methods: EvalTo( )

examples: [10] [11]

MulMV(Quantity, Quantity, Quantity, Quantity) Quantity

Matrix-Vector product: MulMV(AX, AY, AZ, m) = (AX·m, AY·m, AZ·m). The arguments Ax, Ay, Az and m are quantities with 3 componets.

methods: EvalTo( )

NeelSkyrmion(int, int) Config

Néél skyrmion magnetization with given charge and core polarization

methods: Add( float64 Config ) RotZ( float64 ) Scale( float64 float64 float64 ) Transl( float64 float64 float64 )

examples: [5]

NEval

Total number of torque evaluations

methods: Average( ) EvalTo( Slice ) Get( )

NewScalarMask(int, int, int) Slice

Makes a 3D array of scalars

NewSlice(int, int, int, int) Slice

Makes a 4D array with a specified number of components (first argument) and a specified size nx,ny,nz (remaining arguments)

NewVectorMask(int, int, int) Slice

Makes a 3D array of vectors

examples: [15]

NoDemagSpins

Disable magnetostatic interaction per region (default=0, set to 1 to disable). E.g.: NoDemagSpins.SetRegion(5, 1) disables the magnetostatic interaction in region 5.

norm(float64) float64

Standard normal distribution

examples: [5] [12]

Normalized(Quantity) Quantity

Normalize quantity

methods: EvalTo( )

examples: [12]

now() time.Time

Returns the current time

methods: Add( time.Duration ) AddDate( int int int ) After( time.Time ) AppendFormat( []uint8 string ) Before( time.Time ) Clock( ) Date( ) Day( ) Equal( time.Time ) Format( string ) GobEncode( ) Hour( ) ISOWeek( ) In( *time.Location ) IsZero( ) Local( ) Location( ) MarshalBinary( ) MarshalJSON( ) MarshalText( ) Minute( ) Month( ) Nanosecond( ) Round( time.Duration ) Second( ) Sub( time.Time ) Truncate( time.Duration ) UTC( ) Unix( ) UnixNano( ) Weekday( ) Year( ) YearDay( ) Zone( )

OpenBC

Use open boundary conditions (default=false)

OutputFormat

Format for data files: OVF1_TEXT, OVF1_BINARY, OVF2_TEXT or OVF2_BINARY

OVF1_BINARY

OutputFormat = OVF1_BINARY sets binary OVF1 output

OVF1_TEXT

OutputFormat = OVF1_TEXT sets text OVF1 output

OVF2_BINARY

OutputFormat = OVF2_BINARY sets binary OVF2 output

OVF2_TEXT

OutputFormat = OVF2_TEXT sets text OVF2 output

PeakErr

Overall maxium error per step

methods: Average( ) EvalTo( Slice ) Get( )

examples: [4] [5] [6] [11] [13] [14] [15]

Pol

Electrical current polarization

examples: [5] [10] [11] [14]

pow(float64, float64) float64

Pow returns x**y, the base-x exponential of y.

examples: [2] [15]

pow10(int) float64

Pow10 returns 10**n, the base-10 exponential of n.

Print(...interface {})

Print to standard output

examples: [2]

rand() float64

Random number between 0 and 1

examples: [3] [5] [12] [15]

randExp() float64

Exponentially distributed random number between 0 and +inf, mean=1

randInt(int) int

Random non-negative integer

randNorm() float64

Standard normal random number

examples: [12]

RandomMag() Config

Random magnetization

methods: Add( float64 Config ) RotZ( float64 ) Scale( float64 float64 float64 ) Transl( float64 float64 float64 )

examples: [3] [5]

RandomMagSeed(int) Config

Random magnetization with given seed

methods: Add( float64 Config ) RotZ( float64 ) Scale( float64 float64 float64 ) Transl( float64 float64 float64 )

randSeed(int)

Sets the random number seed

Rect(float64, float64) Shape

2D rectangle with size in meter

examples: [4] [6] [9] [11] [12] [15]

regions

Outputs the region index for each cell

methods: Average( ) EvalTo( Slice ) GetCell( int int int ) Gpu( ) HostArray( ) HostList( ) LoadFile( string ) SetCell( int int int int )

examples: [7] [12]

Relax()

Try to minimize the total energy

examples: [1] [2] [3] [9] [10] [11]

RelaxTorqueThreshold

MaxTorque threshold for relax(). If set to -1 (default), relax() will stop when the average torque is steady or increasing.

remainder(float64, float64) float64

Remainder returns the IEEE 754 floating-point remainder of x/y.

RemoveCustomFields()

Removes all custom fields again

Run(float64)

Run the simulation for a time in seconds

examples: [1] [7] [10] [11] [12] [14] [15]

RunWhile(func() bool)

Run while condition function is true

Save(Quantity)

Save space-dependent quantity once, with auto filename

examples: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]

SaveAs(Quantity, string)

Save space-dependent quantity with custom filename

examples: [4] [5] [7] [9]

SetCellSize(float64, float64, float64)

Sets the X,Y,Z cell size in meters

examples: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]

SetGeom(Shape)

Sets the geometry to a given shape

examples: [4] [6] [7] [8] [9] [11] [12] [14]

SetGridSize(int, int, int)

Sets the number of cells for X,Y,Z

examples: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]

SetMesh(int, int, int, float64, float64, float64, int, int, int)

Sets GridSize, CellSize and PBC at the same time

SetPBC(int, int, int)

Sets the number of repetitions in X,Y,Z to create periodic boundary conditions. The number of repetitions determines the cutoff range for the demagnetization.

SetSolver(int)

Set solver type. 1:Euler, 2:Heun, 3:Bogaki-Shampine, 4: Runge-Kutta (RK45), 5: Dormand-Prince, 6: Fehlberg, -1: Backward Euler

Shift(int)

Shifts the simulation by +1/-1 cells along X

examples: [15]

Shifted(Quantity, int, int, int) Quantity

Shifted quantity

methods: EvalTo( )

ShiftGeom

Whether Shift() acts on geometry

ShiftM

Whether Shift() acts on magnetization

examples: [15]

ShiftMagD

Upon shift, insert this magnetization from the bottom

methods: Add( data.Vector ) Cross( data.Vector ) Div( float64 ) Dot( data.Vector ) Len( ) MAdd( float64 data.Vector ) Mul( float64 ) Sub( data.Vector ) X( ) Y( ) Z( )

ShiftMagL

Upon shift, insert this magnetization from the left

methods: Add( data.Vector ) Cross( data.Vector ) Div( float64 ) Dot( data.Vector ) Len( ) MAdd( float64 data.Vector ) Mul( float64 ) Sub( data.Vector ) X( ) Y( ) Z( )

ShiftMagR

Upon shift, insert this magnetization from the right

methods: Add( data.Vector ) Cross( data.Vector ) Div( float64 ) Dot( data.Vector ) Len( ) MAdd( float64 data.Vector ) Mul( float64 ) Sub( data.Vector ) X( ) Y( ) Z( )

examples: [15]

ShiftMagU

Upon shift, insert this magnetization from the top

methods: Add( data.Vector ) Cross( data.Vector ) Div( float64 ) Dot( data.Vector ) Len( ) MAdd( float64 data.Vector ) Mul( float64 ) Sub( data.Vector ) X( ) Y( ) Z( )

ShiftRegions

Whether Shift() acts on regions

Sign(float64) float64

Signum function

sin(float64) float64

Sin returns the sine of the radian argument x.

examples: [5] [6] [13] [14] [15]

sinc(float64) float64

Sinc returns sin(x)/x. If x=0, then Sinc(x) returns 1.

since(time.Time) time.Duration

Returns the time elapsed since argument

methods: Hours( ) Microseconds( ) Milliseconds( ) Minutes( ) Nanoseconds( ) Round( time.Duration ) Seconds( ) Truncate( time.Duration )

sinh(float64) float64

Sinh returns the hyperbolic sine of x.

Snapshot(Quantity)

Save image of quantity

SnapshotAs(Quantity, string)

Save image of quantity with custom filename

SnapshotFormat

Image format for snapshots: jpg, png or gif.

spinAngle

Angle between neighboring spins (rad)

methods: Average( ) EvalTo( Slice ) Region( int )

sprint(...interface {}) string

Print all arguments to string with automatic formatting

sprintf(string, ...interface {}) string

Print to string with C-style formatting.

sqrt(float64) float64

Sqrt returns the square root of x.

examples: [2]

Square(float64) Shape

2D square with size in meter

examples: [6]

step

Total number of time steps taken

examples: [3] [10]

Steps(int)

Run the simulation for a number of time steps

STTorque

Spin-transfer torque/γ0 (T)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

Total simulated time (s)

examples: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]

TableAdd(Quantity)

Add quantity as a column to the data table.

examples: [3] [11] [13]

TableAddVar(ScalarFunction, string, string)

Add user-defined variable + name + unit to data table.

TableAutoSave(float64)

Auto-save the data table every period (s). Zero disables save.

examples: [1] [11] [14]

TablePrint(...interface {})

Print anyting in the data table

TableSave()

Save the data table right now (appends one line).

examples: [3] [13]

tan(float64) float64

Tan returns the tangent of the radian argument x.

tanh(float64) float64

Tanh returns the hyperbolic tangent of x.

Temp

Temperature (K)

ThermSeed(int)

Set a random seed for thermal noise

torque

Total torque/γ0 (T)

methods: Average( ) Comp( int ) EvalTo( Slice ) HostCopy( ) Region( int )

TotalShift

Amount by which the simulation has been shifted (m).

true

trunc(float64) float64

Trunc returns the integer value of x.

TwoDomain(float64, float64, float64, float64, float64, float64, float64, float64, float64) Config

Twodomain magnetization with with given magnetization in left domain, wall, and right domain

methods: Add( float64 Config ) RotZ( float64 ) Scale( float64 float64 float64 ) Transl( float64 float64 float64 )

examples: [5] [10] [11]

Uniform(float64, float64, float64) Config

Uniform magnetization in given direction

methods: Add( float64 Config ) RotZ( float64 ) Scale( float64 float64 float64 ) Transl( float64 float64 float64 )

examples: [1] [2] [5] [6] [7] [13] [14] [15]

Universe() Shape

Entire space

Vector(float64, float64, float64) data.Vector

Constructs a vector with given components

methods: Add( data.Vector ) Cross( data.Vector ) Div( float64 ) Dot( data.Vector ) Len( ) MAdd( float64 data.Vector ) Mul( float64 ) Sub( data.Vector ) X( ) Y( ) Z( )

examples: [1] [3] [5] [7] [10] [11] [12] [14] [15]

Vortex(int, int) Config

Vortex magnetization with given circulation and core polarization

methods: Add( float64 Config ) RotZ( float64 ) Scale( float64 float64 float64 ) Transl( float64 float64 float64 )

examples: [5] [8] [9] [12]

VortexWall(float64, float64, int, int) Config

Vortex wall magnetization with given mx in left and right domain and core circulation and polarization

methods: Add( float64 Config ) RotZ( float64 ) Scale( float64 float64 float64 ) Transl( float64 float64 float64 )

examples: [5]

Non-adiabaticity of spin-transfer-torque

examples: [10] [11] [12]

XRange(float64, float64) Shape

Part of space between x1 (inclusive) and x2 (exclusive), in meter

examples: [4] [7]

y0(float64) float64

Y0 returns the order-zero Bessel function of the second kind.

y1(float64) float64

Y1 returns the order-one Bessel function of the second kind.

yn(int, float64) float64

Yn returns the order-n Bessel function of the second kind.

YRange(float64, float64) Shape

Part of space between y1 (inclusive) and y2 (exclusive), in meter

ZRange(float64, float64) Shape

Part of space between z1 (inclusive) and z2 (exclusive), in meter

mumax3.10 API

Basics

Advanced Features

^↑ Back to top ^↑

Syntax

Defining variables

Arithmetic

Control structures

Implicit functions

Methods

Mesh size and geometry

Periodic boundary conditions

Resizing the mesh

Setting the geometry

Shapes

Material regions

Initial magnetization

Material parameters

Excitation

Spin currents

Zhang-Li model

Slonczewski model

Magnetic Force Microscopy

Output quantities

Averaging behavior

Slicing and dicing output

Scheduling output

Running

Relax

Minimize

Moving simulation window

Extensions

Custom quantities

Custom effective field terms

Misc

mumax3.10 API

Basics

Advanced Features

↑ Back to top ↑

Syntax

Defining variables

Arithmetic

Control structures

Implicit functions

Methods

Mesh size and geometry

Periodic boundary conditions

Resizing the mesh

Setting the geometry

Shapes

Material regions

Initial magnetization

Material parameters

Excitation

Spin currents

Zhang-Li model

Slonczewski model

Magnetic Force Microscopy

Output quantities

Averaging behavior

Slicing and dicing output

Scheduling output

Running

Relax

Minimize

Moving simulation window

Extensions

Custom quantities

Custom effective field terms

Misc

^↑ Back to top ^↑