.. module:: magnumfe

Miscellaneous
=============

Units
+++++

The following table contains a list of quantities used in magnum.fe and their units. Note that all quantities are given in SI units.

This convention also applies to the mesh dimension which in general is expected to be given in meters. However, for numerical reasons it is preferable to create a mesh with lateral dimensions with the order of magnitude 1 and add a proper :code:`scale` parameter in the :class:`State` class. Usually nanometers are a good choice which corresponds to :code:`state.scale = 1e-9`.

======================================  ===================================================  =============================
**Quantity**                            **Description**                                      **Unit**
======================================  ===================================================  =============================
:code:`A` (:class:`SAFLayer`)           coupling constant                                    :math:`\text{J/m}^2`
:code:`A` (:class:`AFCoupling`)         coupling constant                                    :math:`\text{J/m}^2`
:code:`Aex` (:class:`Material`)         exchange constant                                    :math:`\text{J/m}`
:code:`alpha` (:class:`Material`)       damping constant                                     :math:`1`
:code:`b` (:class:`Material`)           coupling constant (Zhang and Li model)               :math:`\text{m}^3/\text{As}`
:code:`beta` (:class:`Material`)        polarization parameter                               :math:`1`
:code:`beta_prime` (:class:`Material`)  polarization parameter                               :math:`1`
:code:`c` (:class:`Material`)           spin diffusion coupling constant (deprecated)        :math:`\text{N/A}^2`
:code:`C0` (:class:`Material`)          connected to conductivity by :math:`C_0=\sigma/2`    :math:`\text{A/Vm}`
:code:`D0` (:class:`Material`)          diffusion constant                                   :math:`\text{m}^2\text{/s}`
:code:`D_inter` (:class:`Material`)     interface DMI coupling constant                      :math:`\text{J/m}^2`
:code:`E()` (:class:`LLGTerm`)          energy                                               :math:`\text{J}`
:code:`h()` (:class:`LLGTerm`)          field                                                :math:`\text{A/m}`
:code:`j` (:class:`State`)              electric current                                     :math:`\text{A/m}^2`
:code:`J` (:class:`Material`)           coupling strength                                    :math:`\text{J}`
:code:`K_uni` (:class:`Material`)       anisotropy constant                                  :math:`\text{J/m}^3`
:code:`lambda_sf` (:class:`Material`)   diffusion length (deprecated)                        :math:`\text{m}`
:code:`lambda_j` (:class:`Material`)    diffusion length (deprecated)                        :math:`\text{m}`
:code:`m` (:class:`State`)              magnetization                                        :math:`1`
:code:`ms` (:class:`Material`)          saturation magnetization                             :math:`\text{A/m}`
:code:`s` (:class:`State`)              spin accumulation                                    :math:`\text{A/m}`
:code:`sigma` (:class:`Material`)       electric conductivity                                :math:`\text{A/Vm}`
:code:`t` (:class:`State`)              time                                                 :math:`\text{s}`
:code:`T` (:class:`State`)              temperature                                          :math:`\text{K}`
:code:`theta` (:class:`Material`)       spin Hall angle                                      :math:`1`
:code:`tau_sf` (:class:`Material`)      spin-flip relaxation time                            :math:`\text{s}`
:code:`xi` (:class:`Material`)          degree of nonadiabacity (Zhang and Li model)         :math:`1`
======================================  ===================================================  =============================

:class:`Constants`
++++++++++++++++++

magnum.fe defines some important constants in the :class:`Constants` class. They can be used to conveniently convert units. For instance the field strength of 2 Tesla can be converted to A/m by using :code:`2.0 / Constants.mu0` in the simulation script.

.. autoclass:: Constants
   :members:

:func:`read_vtk`
++++++++++++++++

.. autofunction:: read_vtk

:class:`TimeInterpolator`
+++++++++++++++++++++++++

.. autoclass:: TimeInterpolator
   :members:

:class:`Timer`
++++++++++++++

.. autoclass:: Timer
   :members:

:class:`Cache`
++++++++++++++

.. autoclass:: Cache
   :members:

Screen logging
++++++++++++++

magnum.fe uses the Python :code:`logging` interface to print status information to the screen. The verbosity of the screen logging can be configured for magnum.fe and third party libraries individualy. Availabe log levels are

.. code:: python

  CRITICAL  = 50 # errors that may lead to data corruption and suchlike
  ERROR     = 40 # things that go boom
  WARNING   = 30 # things that may go boom later
  INFO      = 20 # information of general interest

.. autofunction:: set_log_level
.. autofunction:: set_fenics_log_level