def setup(self):
nf = self.norm_factor
# Create the material for Fe2 in DyFe2 and YFe2
# A unique material can be used because the iron moment per unit volume
# in DyFe2 and YFe2 are the same.
# NOTE: The demagnetising field acts as a shape anisotropy in the 1D model:
# H_demag = -M_x which can be expressed as an uniaxial anisotropy
# H_demag = (2 K_1 m*u) / (mu0*M_sat)
# where the axis u = (1, 0, 0) and K_1 = -mu0*M_sat^2/2
# NOTE: Strictly this is wrong
demag_Fe2 = \
nmag.uniaxial_anisotropy(axis=[1, 0, 0],
K1=-self.enable_demag*0.5*mu0*self.Ms_Fe2**2)
mat_Fe2 = \
nmag.MagMaterial(name="Fe2",
Ms=self.Ms_Fe2,
exchange_coupling=self.A_Fe2,
anisotropy=demag_Fe2,
llg_normalisationfactor=SI(nf, "1/s"),
llg_damping=SI(self.damping),
llg_polarisation=SI(self.P),
llg_xi=SI(self.xi))
# Create the material
# the sum comes from taking the data from Jurgen's simulations
# where the total moment in DyFe2 is given Ms_DyFe2 = Ms_Dy - Ms_Fe2
cubic_Dy = \
nmag.cubic_anisotropy(axis1=[1, -1, 0],
axis2=[1, 1, 0],
K1=SI(33.853774961e6, "J/m^3"),
K2=SI(-16.1710504363e6, "J/m^3"),
K3=SI(16.3584237059e6, "J/m^3"))
demag_Dy = \
nmag.uniaxial_anisotropy(axis=[1, 0, 0],
K1=-self.enable_demag*0.5*mu0*self.Ms_Dy**2)
mat_Dy = \
nmag.MagMaterial(name="Dy",
Ms=self.Ms_Dy,
exchange_coupling=SI(0.0e-12, "J/m"),
anisotropy=demag_Dy + cubic_Dy,
llg_normalisationfactor=SI(nf, "1/s"),
llg_damping=SI(self.damping),
llg_polarisation=0.0)
#--------------------------------------------
## Here we set up the simulation
# Create the simulation object
sim = nmag.Simulation(self.sim_name, do_demag=False,
adjust_tolerances=False)
# Set the coupling between the two magnetisations
#sim.set_local_magnetic_coupling(mat_Fe2, mat_Dy, SI(-2.2337e-4, "N/A^2"))
sim.set_local_magnetic_coupling(mat_Fe2, mat_Dy, self.A_lc)
x0 = self.width_soft*0.5
x1 = x0 + self.width_hard
layers = [(-x1, -x0), (-x0, x0), (x0, x1)]
mat_allocation = [("DyFe2_up", [mat_Dy, mat_Fe2]),
("YFe2", mat_Fe2),
("DyFe2_down", [mat_Dy, mat_Fe2])]
# Creates the mesh from the layer structure
if not os.path.exists(self.mesh_file_name) or self.new_mesh:
print "Creating the mesh"
mesh_lists = unidmesher.mesh_1d(layers, self.discretization)
unidmesher.write_mesh(mesh_lists, out=self.mesh_file_name)
sim.load_mesh(self.mesh_file_name, mat_allocation, unit_length=SI(1e-9, "m"))
self.sim = sim
return sim
# Create the simulation object
sim = nmag.Simulation(name, do_demag=False)
# Load the mesh
sim.load_mesh("bar.nmesh.h5", [("Py", mat_Py)], unit_length=SI(1e-9, "m"))
# Set the initial magnetisation
sim.set_m(lambda r: m_gen(np.array(r) * 1e9))
#sim.advance_time(SI(1e-12, 's') )
# Save the exchange field and the magnetisation once at the beginning
# of the simulation for comparison with finmag
np.savetxt("H_%s_nmag.txt" % name, sim.get_subfield("H_anis_Py"))
np.savetxt("m0_nmag.txt", sim.get_subfield("m_Py"))
if __name__ == "__main__":
# define uniaxial_anisotropy
anis = nmag.uniaxial_anisotropy(axis=[1, 0, 0],
K1=SI(520e3, "J/m^3"),
K2=SI(230e3, "J/m^3"))
generate_anisotropy_data(anis)
cubic = nmag.cubic_anisotropy(axis1=[1, 0, 0],
axis2=[0, 1, 0],
K1=SI(520e3, "J/m^3"),
K2=SI(230e3, "J/m^3"),
K3=SI(123e3, "J/m^3"))
generate_anisotropy_data(cubic, name='cubic_anis')
import nmag
from nmag import SI, si
# Create the simulation object
sim = nmag.Simulation()
# Define the magnetic material (data from OOMMF materials file)
Fe = nmag.MagMaterial(name="Fe",
Ms=SI(1700e3, "A/m"),
exchange_coupling=SI(21e-12, "J/m"),
anisotropy=nmag.cubic_anisotropy(axis1=[1, 0, 0],
axis2=[0, 1, 0],
K1=SI(48e3, "J/m^3")))
# Load the mesh
sim.load_mesh("cube.nmesh", [("cube", Fe)], unit_length=SI(1e-9, "m"))
# Set the initial magnetisation
sim.set_m([0, 0, 1])
# Launch the hysteresis loop
Hs = nmag.vector_set(direction=[1.0, 0, 0.0001],
norm_list=[0, 1, [], 19, 19.1, [], 21, 22, [], 50],
units=0.001*si.Tesla/si.mu0)
sim.hysteresis(Hs)
Ms=Ms_Fe2,
exchange_coupling=SI(14.6e-12, "J/m"),
anisotropy=uni_anis,
llg_normalisationfactor=SI(0.001e12, "1/s"),
llg_damping=llg_damping,
llg_polarisation=SI(1.0))
# Create the material
Ms_DyFe2 = SI(1.18085121013e6, "A/m")
Ms_Dy = Ms_DyFe2 + Ms_Fe2
# the sum comes from taking the data from Jurgen's simulations
# where the total moment in DyFe2 is given Ms_DyFe2 = Ms_Dy - Ms_Fe2
cubic_Dy = \
nmag.cubic_anisotropy(axis1=[1,0,-1],
axis2=[1,0,1],
K1=SI(33.853774961e6, "J/m^3"),
K2=SI(-16.1710504363e6, "J/m^3"),
K3=SI(16.3584237059e6, "J/m^3"))
demag_Dy = nmag.uniaxial_anisotropy(axis=[1, 0, 0], K1=-0.5*mu0*Ms_Dy**2)
mat_Dy = \
nmag.MagMaterial(name="Dy",
Ms=Ms_Dy,
exchange_coupling=SI(0.0e-12, "J/m"),
anisotropy=demag_Dy + cubic_Dy,
llg_normalisationfactor=SI(0.001e12, "1/s"),
llg_damping=llg_damping)
#This is the expression returned by the sampler:
#E_anis_Dy=
# 4.23260765 m_Dy(1)^8
