Beispiel #1
0
import math
from nmag.common import SI, degrees_per_ns, Tesla, mu0, at, every
from nmag.nmag5 import Simulation, MagMaterial

# Applied field
Happ_dir = [0, 0, 10]  # in mT

# Material definition
mat = MagMaterial("Py", Ms=SI(860e3, "A/m"),
                  exchange_coupling=SI(13e-12, "J/m"),
                  llg_gamma_G=SI(221017, "m/s A"),
                  llg_damping=SI(0.014))

sim = Simulation("nmag_no_stt", do_demag=False)
nm = SI(1e-9, "m")
sim.load_mesh("mesh.nmesh", [("cube", mat)], unit_length=nm)
sim.set_m([1, 0.01, 0.01])
sim.set_H_ext(Happ_dir, 0.001 * Tesla / mu0)

# Define the tolerances for the simulation
ns = SI(1e-9, "s")
sim.set_params(stopping_dm_dt=0 * degrees_per_ns,
               ts_rel_tol=1e-8, ts_abs_tol=1e-8,
               ts_pc_rel_tol=1e-3, ts_pc_abs_tol=1e-8,
               demag_dbc_rel_tol=1e-6, demag_dbc_abs_tol=1e-6)
sim.relax(save=[("averages", every("time", 0.01 * ns))],
          do=[("exit", at("time", 10 * ns))])
Beispiel #2
0
  v = (1.0e-9, dz, -dy)
  vn = (1.0e-9**2 + dy*dy + dz*dz)**0.5
  return tuple(vi/vn for vi in v)

sim.set_m(m0)

sim.set_H_ext([0, 0, 0], SI("A/m"))

# Direction of the polarization
sim.model.quantities["sl_fix"].set_value(Value([0, 1, 0]))

# Current density
sim.model.quantities["sl_current_density"].set_value(Value(SI(0.1e12, "A/m^2")))


if do_relaxation:
  print "DOING RELAXATION"
  sim.relax(save=[("fields", at("time", 0*ps) | at("convergence"))])
  sim.save_m_to_file(relaxed_m)
  sys.exit(0)

else:
  print "DOING DYNAMICS"
  sim.load_m_from_h5file(relaxed_m)
  sim.set_params(stopping_dm_dt=0*degrees_per_ns)
  sim.relax(save=[("averages", every("time", 5*ps))],
            do=[("exit", at("time", 10000*ps))])

#ipython()

Beispiel #3
0
                  llg_damping=SI(0.014),
                  anisotropy=anis)

mat.sl_P = 0.4             # Polarisation
mat.sl_lambda = 2.0        # lambda parameter
mat.sl_d = SI(5.0e-9, "m") # Free layer thickness

sim = Simulation(do_sl_stt=True, do_demag=False)
sim.load_mesh(mesh_filename, [("region1", mat)], unit_length=nm)
sim.set_m([1, 0.01, 0.01])
sim.set_H_ext(Happ_dir, 0.001*Tesla/mu0)

# Direction of the polarization
theta_rad = math.pi*theta/180.0
phi_rad = math.pi*phi/180.0
P_direction = [math.sin(theta_rad)*math.cos(phi_rad),
               math.sin(theta_rad)*math.sin(phi_rad),
               math.cos(theta_rad)]

# Set the polarization direction and current density
sim.model.quantities["sl_fix"].set_value(Value(P_direction))
sim.model.quantities["sl_current_density"].set_value(Value(current_density))

# Define the tolerances for the simulation
sim.set_params(stopping_dm_dt=0*degrees_per_ns,
               ts_rel_tol=1e-8, ts_abs_tol=1e-8,
               ts_pc_rel_tol=1e-3, ts_pc_abs_tol=1e-8,
               demag_dbc_rel_tol=1e-6, demag_dbc_abs_tol=1e-6)
sim.relax(save=[("averages", every("time", 5*ps))],
          do=[("exit", at("time", 10000*ps))])
Beispiel #4
0
    v = (1.0e-9, dz, -dy)
    vn = (1.0e-9**2 + dy * dy + dz * dz)**0.5
    return tuple(vi / vn for vi in v)


sim.set_m(m0)

sim.set_H_ext([0, 0, 0], SI("A/m"))

# Direction of the polarization
sim.model.quantities["sl_fix"].set_value(Value([0, 1, 0]))

# Current density
sim.model.quantities["sl_current_density"].set_value(Value(SI(0.1e12,
                                                              "A/m^2")))

if do_relaxation:
    print "DOING RELAXATION"
    sim.relax(save=[("fields", at("time", 0 * ps) | at("convergence"))])
    sim.save_m_to_file(relaxed_m)
    sys.exit(0)

else:
    print "DOING DYNAMICS"
    sim.load_m_from_h5file(relaxed_m)
    sim.set_params(stopping_dm_dt=0 * degrees_per_ns)
    sim.relax(save=[("averages", every("time", 5 * ps))],
              do=[("exit", at("time", 10000 * ps))])

# ipython()
Beispiel #5
0
              llg_damping=0.5,
              llg_gamma_G=SI(0.2211e6, "m/A s"))

# Create the simulation object
sim = Simulation()

# We want some constants to be spatially dependent
sim.declare("spacefield", "alpha", "Ms", "gamma_G", "exchange_factor")
anisotropy.declare("spacefield", "K1")

# Load the mesh
mats = [("bottom", mag), ("top", mag)]
sim.load_mesh("spatially.nmesh.h5", mats, unit_length=SI(1e-9, "m"))

# Set additional parameters for the time-integration
sim.set_params(stopping_dm_dt=1*degrees_per_ns,
               ts_rel_tol=1e-6, ts_abs_tol=1e-6)

sim.set_m([0.1, 0.1, 1])
sim.set_H_ext([1, 0, 0], SI(100000, 'A/m'))

def create_setter(value_bottom, value_top, value_middle=None):
  # Fields in Nmag are defined on the nodes, which means that it is not
  # straightforward to decide how to set fields at the boundary. Here we
  # decide to set them as half of the values they have on each side.
  value_middle = \
    ([0.5*(v + value_top[i]) for i, v in enumerate(value_bottom)]
      if hasattr(value_top, "__iter__")
      else 0.5*(value_top + value_bottom))

  def setter(position):
    x, y, z = position