default-settings.yml

# FeeLLGood default configuration parameters.

# This file documents the default configuration parameters used by
# feeLLGood. It has the format and structure feeLLGood expects from the
# user-supplied configuration file. It can thus be used as a template.
#
# The file format is YAML. Everything after a ‘#’ character is a
# comment. Settings are organized in sections (YAML “objects”) which are
# defined by the indentation, e.g:
#
#   outputs:                # ‘outputs’ section
#     file_basename: foo    # a setting in the ‘outputs’ section
#   mesh:                   # ‘mesh’ section
#     filename: foo.msh     # a setting in the ‘mesh’ section
#     volume_regions:       # a sub-section of ‘mesh’
#       main_volume:        # a sub-section of ‘volume_regions’
#         Ae: 1.5e-11       # a setting in the ‘main_volume’ section
#
# For a short primer on the YAML syntax, see
# https://getopentest.org/reference/yaml-primer.html
#
# Some numeric values are unit-less, like the reduced magnetization. All
# other values are in SI units.
#
# Unit vectors need not be of unit length: they will be normalized by
# feeLLGood upon reading the file.

# The ‘outputs’ section defines what data will be saved by feeLLGood,
# and in which files.
outputs:

  # Directory where the output files will be stored. The default value
  # (.) means the working directory where the feeLLGood process is
  # started. If the directory does not exist, it will be created.
  directory: .

  # This string will be used as a prefix for the names of all generated
  # files. Defaults to the base name of the mesh file.
  file_basename:

  # The global quantities listed under ‘evol_columns’ will be saved to
  # the evolution file on this time step.
  evol_time_step: 5e-13

  # Time at which to terminate the simulation.
  final_time: 1e-10

  # Global quantities that should be periodically saved to the evolution
  # file. In addition to the defaults below, the following quantities
  # are also available:
  # - iter: iteration number
  # - dt: time step
  # - max_dm: maximum variation of the magnetization
  # - <dMx/dt>: average change rate of Mx
  # - <dMy/dt>: average change rate of My
  # - <dMz/dt>: average change rate of Mz
  # - E_aniso: anisotropy energy
  # - Hx: applied field along x
  # - Hy: applied field along y
  # - Hz: applied field along z
  evol_columns:
    - t         # time
    - <Mx>      # Average value of Mx
    - <My>      # Average value of My
    - <Mz>      # Average value of Mz
    - E_ex      # Exchange energy
    - E_demag   # Demagnetizing energy
    - E_zeeman  # Zeeman energy
    - E_tot     # Total energy

  # How often to save the magnetization configuration. This should be
  # either an integer that is interpreted in units of ‘evol_time_step’,
  # or the keyword ‘false’ which disables the feature.
  mag_config_every: 100

# Description of the meshed object.
mesh:

  # Name of the file containing the mesh. As there is no valid default,
  # the user must provide this in their configuration file.
  filename:

  # Unit of length used in the mesh file, in meters.
  length_unit: 1e-9

  # Material parameters of the volume regions defined by the mesh. Each
  # region is defined as a subsection of ‘volume_regions’.
  volume_regions:

    # Defaults that apply to all regions. Note that ‘__default__’ is not
    # a valid region name: it is a placeholder for the defaults. In the
    # user-supplied configuration file, ‘__default__’ should be replaced
    # by the region name.
    __default__:

      # Exchange constant.
      Ae: 1e-11

      # Saturation magnetization times µ₀, in tesla.
      Js: 1

      # Second order magnetocrystalline anisotropy constant.
      K: 0

      # Unit vector defining the anisotropy axis.
      uk: [0, 0, 1]

      # Cubic magnetocrystalline anisotropy constant.
      K3: 0

      # Unit vectors along the principal directions of the cubic
      # anisotropy.
      ex: [1, 0, 0]
      ey: [0, 1, 0]
      ez: [0, 0, 1]

      # Dimensionless damping parameter.
      alpha_LLG: 0.5

  # Material parameters of the surface regions defined by the mesh.
  surface_regions:

    # Defaults that apply to all regions. Again, ‘__default__’ is a
    # placeholder, not a valid region name.
    __default__:

      # Whether the magnetic charges on this surface should be removed,
      # in order to simulate an infinite medium.
      suppress_charges: false

      # Second order surface anisotropy constant.
      Ks: 0

      # Unit vector along the surface anisotropy axis.
      uk: [0, 0, 1]

# The initial magnetization can be provided as either:
# - the name of a file in feeLLGood’s format (‘.sol’ file)
# - an array of three expression depending on the Cartesian spatial
#   coordinates (x, y, z); the expression may be constants.
initial_magnetization: [0, 0, 1]

# Initial time of the simulation. Default is:
# - the time recorded in the ‘.sol’ file providing the initial
#   magnetization, if the initial magnetization was defined this way
# - zero otherwise
initial_time:

# “Recentering” is the process by which feeLLGood tries to artificially
# keep a domain wall in the center of the simulated volume by
# translating the magnetization vector field.
recentering:

  # Whether to enable recentering.
  enable: false

  # Direction along which to translate the magnetization field. Should
  # be either ‘X’, ‘Y’ or ‘Z’.
  direction: Z

  # Threshold on the absolute value of the reduced magnetization above
  # which to trigger the translation.
  threshold: 0.1

# Expressions of the applied field, as a function of t, the time in
# seconds. May be constants.
Bext: [0, 0, 0]

# Parameters for simulating a spin transfer torque. This is a work in
# progress, not ready for general use.
spin_transfer_torque:
  enable: false
  sigma: 1.0
  dens_state: 1.0
  beta: 0
  l_J: 1.0
  l_sf: 1.0
  V_file: false

# Parameters for the computation of the demagnetizing field.
demagnetizing_field_solver:

  # Number of threads to use. The value 0 means to match the number of
  # available processors (actually, hardware threads), as reported by
  # sysconf(_SC_NPROCESSORS_ONLN).
  nb_threads: 0

# Parameters of the solver.
finite_element_solver:

  # Number of threads to use. The value 0 means to match the number of
  # available processors.
  nb_threads: 0

  # Maximum number of iteration for the biconjugate gradient algorithm.
  max(iter): 500

  # solver tolerance.
  tolerance: 1e-6

  # ILU preconditioner tolerance
  ILU_tolerance: 1e-2

  # ILU preconditioner filling factor
  ILU_fill_factor: 10

# Parameters for the integration of the dynamic equation.
time_integration:

  # Limit on the maximum variation of the reduced magnetization in a
  # single time step.
  max(du): 0.02

  # Minimal time step. If the solver cannot converge with this time
  # step, the simulation will be aborted.
  min(dt): 1e-16

  # Maximal time step.
  max(dt): 5e-13