ZhangLi#

class micromagneticmodel.ZhangLi(**kwargs)#

Zhang-Li spin transfer torque dynamics term.

\[\frac{\text{d}\mathbf{m}}{\text{d}t} = -\frac{1+\alpha\beta}{1+\alpha^{2}} \mathbf{m} \times (\mathbf{m} \times (\mathbf{u} \cdot \boldsymbol\nabla) \mathbf{m}) - \frac{\beta - \alpha}{1+\alpha^{2}} \mathbf{m} \times (\mathbf{u} \cdot \boldsymbol\nabla)\mathbf{m}\]

A time-dependent current can be specified by providing a time-dependent pre-factor that is used to multiply u. The time-dependence can either be specified by providing a callable func that is evaluated at time steps dt or by passing a dictionary tcl_strings of tcl strings that are written to the mif file.

Parameters:

beta (numbers.Real) – A single scalar value can be passed.
u (number.Real, discretisedfield.Field) – numbers.Real can be passed, or alternatively discretisedfield.Field can be passed.
func (callable, optional) – Callable to define arbitrary time-dependence, multiplies u. Called at times that are multiples of dt. Must return a single number.
dt (numbers.Real, optional (required for func)) – Time steps in seconds to evaluate callable func at.
tcl_strings (dict, optional) – Dictionary of tcl strings to be included into the mif file for more control over specific time-dependencies. Must contain the following keys: script, script_args, and script_name. Refer to the OOMMF documentation for more details (behaves similar to Slonczewski current/Oxs_SpinXferEvolve: https://math.nist.gov/oommf/doc/userguide20a3/userguide/Standard_Oxs_Ext_Child_Clas.html#SX).

Examples

Defining the Zhang-Li dynamics term using scalar.

>>> import micromagneticmodel as mm
...
>>> zhangli = mm.ZhangLi(beta=0.01, u=5e6)

Defining the Zhang-Li dynamics term using discretisedfield.Field.

>>> import discretisedfield as df
...
>>> region = df.Region(p1=(0, 0, 0), p2=(5e-9, 5e-9, 5e-9))
>>> mesh = df.Mesh(region=region, n=(5, 5, 5))
>>> beta = 0.012
>>> u = df.Field(mesh, nvdim=1, value=1e5)
>>> zhangli = mm.ZhangLi(beta=beta, u=u)

Defining a sinusoidal decaying current.

>>> import micromagneticmodel as mm
>>> import numpy as np
...
>>> def sin_wave(t):
...     omega = 2 * np.pi / 1e-9
...     return np.sin(omega * t)
>>> zhangli = mm.ZhangLi(beta=0.01, u=5e6, func=sin_wave, dt=1e-13)

An attempt to define the Zhang-Li dynamics term using a wrong value (here using a vector u where a scalar value is required).

>>> zhangli = mm.ZhangLi(beta=-1, u=(0, 0, 1))  # vector value
Traceback (most recent call last):
...
TypeError: ...

Methods

`__add__`	Binary `+` operator.
`__dir__`	Default dir() implementation.
`__eq__`	Relational operator `==`.
`__iter__`	Iterator.
`__repr__`	Representation string.
`dmdt`

Properties

`beta`	Descriptor allowing setting attributes only with scalars (`numbers.Real`).
`dt`	Descriptor allowing setting attributes only with scalars (`numbers.Real`).
`func`	Descriptor allowing setting attributes only with values of a certain type.
`name`	Name.
`tcl_strings`	Descriptor allowing setting attributes with a dictionary, which has keys defined by `key_descriptor` and values defined by `value_descriptor`.
`u`	Descriptor allowing setting attributes with a value described as `descriptor` or a dictionary.