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))])
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)
mat.sl_P = 0.76 # Polarisation
mat.sl_lambda = 2.0 # lambda parameter
mat.sl_d = SI(2.5e-9, "m") # Free layer thickness
sim = Simulation(do_sl_stt=True, do_demag=False)
sim.load_mesh("disc.nmesh.h5", [("region1", mat)], unit_length=nm)
sim.set_m([0.01, 0.01, 1 ])
sim.set_H_ext(Happ_dir, 0.001*Tesla/mu0)
# Direction of the polarization
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()
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()
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))])
# From left to right:
# (1) the name of the parameter to set,
# (2) the units of measurement to use for these last two numbers,
# (3) the value of the parameter on the first layer,
# (4) the value on the second layer.
vs = {"alpha": ( SI(1), 0.5, 0.5), # damping
"Ms": ( SI("A/m"), 0.69e6, 0.80e6), # saturation mag.
"A": ( SI("J/m"), 20e-12, 13.9e-12), # exchange coupling
"K1": (SI("J/m^3"), 4e6, 0.0)} # anisotropy constant
# We need to compute exchange_factor = 2*A/(mu0*Ms)
def exchange_factor(i):
A = vs["A"][0] * vs["A"][1+i]
Ms = vs["Ms"][0] * vs["Ms"][1+i]
return -float((2.0*A/(mu0*Ms))/SI("A m"))
vs["exchange_factor"] = (SI("A m"), exchange_factor(0), exchange_factor(1))
vs.pop("A")
# Set the anisotropy constant K1
units, first, second = vs.pop("K1")
q = anisotropy.quantities["a0_K1"]
q.set_value(Value(create_setter(first, second), units))
# Set all the other quantities
for name, (units, first, second) in vs.iteritems():
q = sim.model.quantities[name]
q.set_value(Value(create_setter(first, second), units))
ps = SI(1e-12, "s")
sim.relax(save=[('fields', every('time', 10*ps))])