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))])
ps = SI(1e-12, "s"); nm = SI(1e-9, "m") # Useful definitions
theta_rad = 3.141592654
phi_rad = 1.570796327
#length, width, thick = (2*nm, 16*nm, 64*nm) # System geometry
current_density = SI( 100e10, "A/m^2") # Applied current
Happ_dir = [0, 0, 0] # Applied field (mT)-
# Material definition
anis = cubic_anisotropy(axis1=[1, 0, 0], axis2=[0,1,0], K1=SI(-1e4, "J/m^3"))
mat = MagMaterial("Co",
Ms=SI(9.0e5, "A/m"),
exchange_coupling=SI(2.0e-11, "J/m"),
llg_gamma_G=SI(2.3245e5, "m/s A"),
llg_damping=SI(0.01),
anisotropy = anis)
relaxed_m = "m0.h5"
film_centre = (5, 50, 50)
do_relaxation = not os.path.exists(relaxed_m)
ps = SI(1e-12, "s")
mat = MagMaterial("Py",
Ms=SI(0.86e6, "A/m"),
exchange_coupling=SI(13e-12, "J/m"),
llg_damping=SI(0.5 if do_relaxation else 0.01))
mat.sl_P = 0.0 if do_relaxation else 0.4 # Polarisation
mat.sl_d = SI(3e-9, "m") # Free layer thickness
sim = Simulation(do_sl_stt=True)
sim.load_mesh(mesh_filename, [("region1", mat)], unit_length=SI(1e-9, "m"))
def m0(r):
dx, dy, dz = tuple(ri - ri0*1e-9 for ri, ri0 in zip(r, film_centre))
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
relaxed_m = "m0.h5"
film_centre = (5, 50, 50)
do_relaxation = not os.path.exists(relaxed_m)
ps = SI(1e-12, "s")
mat = MagMaterial("Py",
Ms=SI(0.86e6, "A/m"),
exchange_coupling=SI(13e-12, "J/m"),
llg_damping=SI(0.5 if do_relaxation else 0.01))
mat.sl_P = 0.0 if do_relaxation else 0.4 # Polarisation
mat.sl_d = SI(10e-9, "m") # Free layer thickness
sim = Simulation(do_sl_stt=True)
sim.load_mesh(mesh_filename, [("region1", mat)], unit_length=SI(1e-9, "m"))
def m0(r):
dx, dy, dz = tuple(ri - ri0 * 1e-9 for ri, ri0 in zip(r, film_centre))
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]))
# Material definition
anis = uniaxial_anisotropy(axis=[0, 0, 1], K1=-SI(0.1e6, "J/m^3"))
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),
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
Ms=SI(0.5e6, "A/m"),
exchange_coupling=SI(13e-12, "J/m"),
anisotropy=anisotropy,
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__")