def main():
MODULE_DIR = os.path.dirname(os.path.abspath(__file__))
L = 10
mesh_unit = SI(1e-9, "m") # mesh unit (1 nm)
layers = [(0.0, L)] # the mesh
discretization = 0.1 # discretization
# Initial magnetization
xfactor = float(SI("m") / (L * mesh_unit))
def m0(r):
return [
np.cos(r[0] * np.pi * xfactor),
np.sin(r[0] * np.pi * xfactor), 0
]
mat_Py = nmag.MagMaterial(name="Py", Ms=SI(1, "A/m"))
sim = nmag.Simulation("Hans' configuration", do_demag=False)
mesh_file_name = '1d.nmesh'
mesh_lists = unidmesher.mesh_1d(layers, discretization)
unidmesher.write_mesh(mesh_lists, out=mesh_file_name)
sim.load_mesh(mesh_file_name, [("Py", mat_Py)], unit_length=mesh_unit)
sim.set_m(m0)
np.save(os.path.join(MODULE_DIR, "nmag_hansconf.npy"),
sim.get_subfield("E_exch_Py"))
def run_simulation(simname, meshfile, hmatrix=None, tol=0.000001):
T_start = time.time()
sim = nmag.Simulation(name=simname, phi_BEM=hmatrix)
Ni = nmag.MagMaterial(name="Ni",
Ms=SI(493380, "A/m"),
exchange_coupling=SI(7.2e-12, "J/m"),
llg_damping=1.0)
ps = SI(1e-12, "s")
sim.load_mesh(meshfile, [("thinfilm", Ni)], unit_length=SI(1e-9, "m"))
sim.set_m([0.05, 0.02, 1.00])
sim.set_params(ts_abs_tol=tol, ts_rel_tol=tol)
sim.set_H_ext([0, 0, 0], SI('A/m'))
dt = SI(5e-12, "s")
T_end = time.time()
T_setup = T_end - T_start
T_start = time.time()
sim.relax(save=[('averages', every('time', 10 * ps))])
T_end = time.time()
T_sim = T_end - T_start
sim.save_data(['m'])
number_nodes = len(sim.mesh.points)
mem_rss = get_memory_of_process() / 1024.0
return [number_nodes, mem_rss, T_setup, T_sim]
def test_hlib():
with DirectoryOf(__file__):
#delete old data files to avoid failure due to this
def remove_if_exists(filename):
if os.path.exists(filename):
os.remove(filename)
remove_if_exists("plain_dat.ndt")
remove_if_exists("plain_dat.h5")
remove_if_exists("hlib_dat.ndt")
remove_if_exists("hlib_dat.h5")
sim_plain = nmag.Simulation(name='plain')
sim_hlib = nmag.Simulation(name='hlib',
phi_BEM=nmag.default_hmatrix_setup)
res_plain = run_sim(sim_plain)
res_hlib = run_sim(sim_hlib)
# extract x-components of results
hdx1 = [h[0] for h in res_plain]
hdx2 = [h[0] for h in res_hlib]
# Output as of 13 December 2009, svn 6453, HF
#
#for r1,r2 in zip(hdx1,hdx2):
# print r1-r2,(r1-r2)/r1,r1,r2
#
# produces:
# -1.10303013207 3.31174926024e-06 -333065.714037 -333064.611006
# -1.18373466324 3.55403967073e-06 -333067.374849 -333066.191114
# -1.26686538779 3.80361435718e-06 -333068.831071 -333067.564206
# -1.32740328263 3.98536687005e-06 -333069.28218 -333067.954776
# -1.34173143021 4.02840496219e-06 -333067.663951 -333066.32222
# -1.35605957796 4.07144347306e-06 -333066.045723 -333064.689663
# -1.37001170352 4.11335588419e-06 -333064.228355 -333062.858343
# -1.34486746625 4.03791095727e-06 -333060.208727 -333058.863859
# -1.30307299155 3.91246719093e-06 -333056.592671 -333055.289598
# -1.26131784206 3.78713877786e-06 -333052.976414 -333051.715096
# -1.19995578279 3.60291609527e-06 -333051.270434 -333050.070478
# the actual test
for r1, r2 in zip(hdx1, hdx2):
assert (r1 - r2) / float(r1) < 1e-5
def generate_anisotropy_data(anis, name='anis'):
# Create the material
mat_Py = nmag.MagMaterial(name="Py", Ms=SI(Ms, "A/m"), anisotropy=anis)
# 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"))
def run_simulation(sim_name, initial_m, damping, stopping_dm_dt,
j, P=0.0, save=[], do=[], do_demag=True):
# Define the material
mat = nmag.MagMaterial(
name="mat",
Ms=SI(0.8e6, "A/m"),
exchange_coupling=SI(13.0e-12, "J/m"),
llg_damping=damping,
llg_xi=SI(0.01),
llg_polarisation=P)
# Create the simulation object and load the mesh
sim = nmag.Simulation(sim_name, do_demag=do_demag)
sim.load_mesh(mesh_name, [("np", mat)], unit_length=mesh_unit)
# Set the pinning at the top and at the bottom of the nanopillar
def pinning(p):
x, y, z = p
tmp = float(SI(x, "m")/(mesh_unit*hl))
if abs(tmp) >= 0.999:
return 0.0
else:
return 1.0
sim.set_pinning(pinning)
if type(initial_m) == str: # Set the initial magnetisation
sim.load_m_from_h5file(initial_m) # a) from file if a string is provided
else:
sim.set_m(initial_m) # b) from function/vector, otherwise
if j != 0.0: # Set the current, if needed
sim.set_current_density([j, 0.0, 0.0], unit=SI("A/m^2"))
# Set additional parameters for the time-integration and run the simulation
sim.set_params(stopping_dm_dt=stopping_dm_dt,
ts_rel_tol=1e-7, ts_abs_tol=1e-7)
sim.relax(save=save, do=do)
return sim
def run_sim(tol):
"""Function that is called repeatedly with different tolerance values.
Each function call is carrying out one simulation.
"""
mat_Py = nmag.MagMaterial(name="Py",
Ms=SI(0.86e6, "A/m"),
exchange_coupling=SI(13.0e-12, "J/m"),
llg_damping=0.5)
#compose name of simulation to inlude value of tolerance
sim = nmag.Simulation("bar_%.6f" % tol)
sim.load_mesh("bar30_30_100.nmesh.h5", [("Py", mat_Py)],
unit_length=SI(1e-9, "m"))
sim.set_m([1, 0, 1])
#set tolerance (has to be called after set_m())
sim.set_params(ts_abs_tol=tol, ts_rel_tol=tol)
dt = SI(2.5e-12, "s")
timing = 0 #initialise variable to measure execution time
for i in range(0, 121):
timing -= time.time() #start measuring time
sim.advance_time(dt * i) #compute time development for 300ps
timing += time.time() #stop measuring time
#we exclude time required to save data
sim.save_data() #save averages every 2.5 ps
#at end of simulation, write performance data into summary file
f = open('resultsummary.txt', 'a') #open file to append
f.write('%g %d %g\n' % (tol, sim.clock['step'], timing))
f.close()
import nmag
from nmag import SI, every, at
mat_Py = nmag.MagMaterial(name="Py",
Ms=SI(0.86e6, "A/m"),
exchange_coupling=SI(13.0e-12, "J/m"),
llg_damping=0.5,
do_precession=False)
sim = nmag.Simulation("bar_relax2")
sim.load_mesh("bar30_30_100.nmesh.h5", [("Py", mat_Py)],
unit_length=SI(1e-9, "m"))
sim.set_m([1, 0, 1])
ps = SI(1e-12, "s")
sim.relax(save=[('averages',
every('time', 5 * ps)), ('fields', at('convergence'))])
import nmag
from nmag import SI, mesh
import os
mat_Py = nmag.MagMaterial(name="Py",
Ms=SI(1e6, "A/m"),
exchange_coupling=SI(13.0e-12, "J/m"))
#sim = nmag.Simulation()
sim = nmag.Simulation(ddd_use_linalg_machine=True)
sim.set_H_ext([0, 0, 0], SI(1, "A/m"))
meshfile = os.path.join("barmini.nmesh.h5")
if os.path.exists(meshfile):
sim.load_mesh(meshfile, [("PyX", mat_Py)], unit_length=SI(1e-9, "m"))
else:
sim.defregion("Py", mesh.box([0.0, 0.0, 0.0], [20, 20, 80]), mat_Py)
mesh = sim.generate_mesh(
([0.0, 0.0, 0.0], [20.0, 20.0, 80.0]), # bounding box
a0=4.0,
max_steps=10,
unit_length=SI(1e-9, "m"))
mesh.save(meshfile)
def initial_magnetization(xyz, mag_type):
import math
return [math.cos(xyz[2]), math.sin(xyz[2]), 0.0]
import nmag
import time
from nmag import SI
# Create an HMatrix setup object
hms = nmag.HMatrixSetup(nmin=50, eps_aca=1e-5, quadorder=2)
# When creating the simulation object, specify that the BEM hmatrix
# should be set up using the object hms.
sim = nmag.Simulation(phi_BEM=hms)
#specify magnetic material, parameters chosen as in example 1
Py = nmag.MagMaterial(name="Py",
Ms=SI(1e6, "A/m"),
exchange_coupling=SI(13.0e-12, "J/m"))
#load the mesh
sim.load_mesh('sphere.nmesh.h5', [('sphere', Py)], unit_length=SI(1e-9, 'm'))
#set the initial magnetisation
sim.set_m([1, 0, 0])
#save the demagnetisation field
sim.save_data(fields=['H_demag'])
#probe the demagnetisation field at ten points within the sphere
for i in range(-5, 6):
x = i * 1e-9
Hdemag = sim.probe_subfield_siv('H_demag', [x, 0, 0])
print "x=", x, ": H_demag = ", Hdemag
import nmag
from nmag import SI
mat_Py = nmag.MagMaterial(name="Py",
Ms=SI(0.86e6, "A/m"),
exchange_coupling=SI(13.0e-12, "J/m"),
llg_damping=0.5)
sim = nmag.Simulation("bar")
sim.load_mesh("coarse_bar.nmesh.h5", [("Py", mat_Py)],
unit_length=SI(1e-9, "m"))
#sim.load_mesh("bar.nmesh.h5",
# [("Py", mat_Py)],
# unit_length=SI(1e-9,"m"))
sim.set_m([1, 0, 1])
dt = SI(5e-12, "s")
######
# After ten time steps, plot the energy density
# from z=0nm to z=100nm through the center of the body.
######
sim.advance_time(dt * 10)
f = open("nmag_exch_Edensity.txt", "w")
f2 = open("nmag_demag_Edensity.txt", "w")
for i in range(100):
f.write("%g " %
import os
H_x = SI(0.0e6, "A/m")
H_y = SI(0.0e6, "A/m")
H_z = SI(0.0e6, "A/m")
intensive_param_by_name = {"H_x": H_x, "H_y": H_y, "H_z": H_z}
mat_void = nmag.MagMaterial(name="void",
Ms=SI(0.1e6, "A/m"),
exchange_coupling=SI(0.0e-12, "J/m"))
mat_Py = nmag.MagMaterial(name="Py",
Ms=SI(1e6, "A/m"),
exchange_coupling=SI(13.0e-12, "J/m"))
sim = nmag.Simulation("sphere", mesh_unit_length=SI(1e-9, "m"), fem_only=False)
meshfile = "sphere-fem-bem.nmesh.h5"
sim.load_mesh(meshfile, [("Py", mat_Py)])
sim.save_mesh("/tmp/debug.mesh")
def initial_magnetization(coords, mag_type):
if coords[0] > 0:
return [1, 0, 0]
else:
return [-1, 0, 0]
sim.set_magnetization(initial_magnetization)
#import ocaml
#print "DDD SPEEDTEST: ",ocaml.ddd_speedtest_lindholm(939*939*2)
time_total = -time.time()
time_writing = 0.0
time_initialising = -time.time()
mat_Py = nmag.MagMaterial(
name="Py",
Ms=SI(0.86e6, "A/m"),
exchange_coupling=SI(13.0e-12, "J/m"),
llg_gamma_G=SI(0.2211e6, "m/A s"),
# llg_damping=SI(0,"")
)
sim = nmag.Simulation(use_pvode=True)
meshfile = "bar30_30_100.nmesh.h5"
sim.load_mesh(meshfile, [("Py", mat_Py)], unit_length=SI(1e-9, "m"))
import math
angle_deg = 45
angle_rad = angle_deg / 360. * 2 * math.pi
sim.set_m([math.cos(angle_rad), 0, math.sin(angle_rad)])
sim.set_params(ts_rel_tol=2.7e-05, ts_abs_tol=2.7e-05)
dt = SI(5e-12, "s")
time_initialising += time.time()
time_loop = -time.time()
import nmag
import time
from nmag import SI
# When creating the simulation object, specify that the BEM hmatrix should be
# set up by using the default parameters.
sim = nmag.Simulation(phi_BEM=nmag.default_hmatrix_setup)
# Specify magnetic material, parameters chosen as in example 1
Py = nmag.MagMaterial(name="Py",
Ms=SI(1e6, "A/m"),
exchange_coupling=SI(13.0e-12, "J/m"))
# Load the mesh
sim.load_mesh('sphere.nmesh.h5', [('sphere', Py)], unit_length=SI(1e-9, 'm'))
# Set the initial magnetisation
sim.set_m([1, 0, 0])
# Save the demagnetisation field
sim.save_data(fields=['H_demag'])
# Probe the demagnetisation field at ten points within the sphere
for i in range(-5, 6):
x = i * 1e-9
Hdemag = sim.probe_subfield_siv('H_demag', [x, 0, 0])
print "x=", x, ": H_demag = ", Hdemag
import time
import nmag
from nmag import SI
start = time.time()
mat_Py = nmag.MagMaterial(name="Py",
Ms=SI(0.86e6,"A/m"),
exchange_coupling=SI(13.0e-12, "J/m"),
llg_damping=0.5)
sim = nmag.Simulation("nmag_bar")
sim.load_mesh("bar.nmesh.h5",
[("Py", mat_Py)],
unit_length=SI(1e-9,"m"))
sim.set_m([1,0,1])
dt = SI(5e-12, "s")
for i in range(0, 61):
sim.advance_time(dt*i) #compute time development
sim.save_data() #save averages
print "Simulation took {:.3} s.".format(time.time() - start)
mz = 0.1
my = (1.0 - (mx * mx * 0.99 + mz * mz)) ** 0.5
return [mx, my, mz]
# Create the material
mat_Py = nmag.MagMaterial(name="Py",
Ms=SI(0.86e6, "A/m"),
exchange_coupling=SI(0, "J/m"), # disables exchange?
anisotropy=nmag.uniaxial_anisotropy(
axis=[0, 0, 1], K1=SI(520e3, "J/m^3")),
llg_gamma_G=SI(0.2211e6, "m/A s"),
llg_damping=SI(0.2),
llg_normalisationfactor=SI(0.001e12, "1/s"))
# Create the simulation object
sim = nmag.Simulation("1d", do_demag=False)
# Creates the mesh from the layer structure
mesh_file_name = '1d.nmesh'
mesh_lists = unidmesher.mesh_1d(layers, discretization)
unidmesher.write_mesh(mesh_lists, out=mesh_file_name)
# Load the mesh
sim.load_mesh(mesh_file_name, [("Py", mat_Py)], unit_length=mesh_unit)
# Set the initial magnetisation
sim.set_m(m0)
# Save the anisotropy field once at the beginning of the simulation
# for comparison with finmag
np.savetxt("anis_t0_ref.txt", sim.get_subfield("H_anis_Py"))
import nmag
from nmag import SI, at
#create simulation object
sim = nmag.Simulation()
# define magnetic material
Py = nmag.MagMaterial(name="Py",
Ms=SI(1e6,"A/m"),
exchange_coupling=SI(13.0e-12, "J/m"))
# load mesh: the mesh dimensions are scaled by 0.5 nm
sim.load_mesh("ellipsoid.nmesh.h5",
[("ellipsoid", Py)],
unit_length=SI(1e-9,"m"))
# set initial magnetisation
sim.set_m([1.,0.,0.])
Hs = nmag.vector_set(direction=[1.,0.01,0],
norm_list=[ 1.00, 0.95, [], -1.00,
-0.95, -0.90, [], 1.00],
units=1e6*SI('A/m'))
# loop over the applied fields Hs
sim.hysteresis(Hs, save=[('restart','fields', at('convergence'))])
)
distrib = None
if ocaml.petsc_is_mpi():
print "MPI!"
print "NODES: ", ocaml.petsc_mpi_nr_nodes()
sys.stdout.flush()
if ocaml.petsc_mpi_nr_nodes() == 2:
distrib = [14280, 14281]
else:
error(
"This example can only run in single-CPU mode or on two machines!")
sim = nmag.Simulation( #temperature=SI(0,"K"),
#thermal_delta_t=SI(1e-14,"s")
)
#meshfile = "bigbar_par.nmesh.h5"
#meshfile = "/tmp/bigmesh10000.mesh"
meshfile = "/tmp/meshbigbar28000nodes.nmesh"
sim.load_mesh(meshfile, [("Py", mat_Py)],
unit_length=SI(1e-9, "m"),
distrib=distrib)
import math
angle_deg = 45
angle_rad = angle_deg / 360. * 2 * math.pi
sim.set_m([math.cos(angle_rad), 0, math.sin(angle_rad)])
from nmag import SI
import nmeshlib.unidmesher as unidmesher
mesh_unit = SI(1e-9, "m") # mesh unit (1 nm)
layers = [(0.0, 1.0)] # the mesh
discretization = 0.2 # discretization
def m0(r):
"""Initial magnetisation 45 degrees between x- and z-axis."""
return [1 / np.sqrt(2), 0, 1 / np.sqrt(2)]
mat_Py = nmag.MagMaterial(name="Py",
Ms=SI(1, "A/m"),
anisotropy=nmag.uniaxial_anisotropy(axis=[0, 0, 1],
K1=SI(
1, "J/m^3")))
sim = nmag.Simulation("Simple anisotropy", do_demag=False)
# Write mesh to file
mesh_file_name = '1d_x6.nmesh'
mesh_lists = unidmesher.mesh_1d(layers, discretization)
unidmesher.write_mesh(mesh_lists, out=mesh_file_name)
sim.load_mesh(mesh_file_name, [("Py", mat_Py)], unit_length=mesh_unit)
sim.set_m(m0)
print sim.get_subfield("E_anis_Py")
# Set Demag tolerances.
ksp_tols = {
"DBC.rtol": 1e-7,
"DBC.atol": 1e-7,
"DBC.maxits": 1000000,
"NBC.rtol": 1e-7,
"NBC.atol": 1e-7,
"NBC.maxits": 1000000,
"PC.rtol": 1e-3,
"PC.atol": 1e-6,
"PC.maxits": 1000000
}
# Create the simulation object
sim = nmag.Simulation(ksp_tolerances=ksp_tols)
# Load the mesh
sim.load_mesh(mesh_name, [("Permalloy", Py)], unit_length=SI(1e-9, "m"))
# Load the initial magnetisation
sim.load_m_from_h5file(relax_name + ".h5")
# Set the applied magnetic field
sim.set_H_ext(H_direction_normalized, SI(H, 'A/m'))
# Set convergence parameters
sim.set_params(stopping_dm_dt=0.0, ts_abs_tol=1e-7, ts_rel_tol=1e-7)
# Save the information ever 5ps, and exit after 20ns.
sim.relax(save=[('fields', every('time', SI(dt, "s")))],
y_lattice = 0.0
z_lattice = 0.0
# list to store the lattice points where the periodic
# copies will be placed
lattice_points = []
for xi in range(-1, 2):
lattice_points.append([xi * x_lattice, 0.0 * y_lattice, 0.0 * z_lattice])
# copies of the system along the x-axis
pbc = nmag.SetLatticePoints(vectorlist=lattice_points,
scalefactor=SI(1e-9, 'm'))
#create simulation object
sim = nmag.Simulation(periodic_bc=pbc.structure)
# load mesh
sim.load_mesh("periodic.nmesh", [("periodic-film", Py)],
unit_length=SI(1e-9, "m"))
print ocaml.mesh_plotinfo_periodic_points_indices(sim.mesh.raw_mesh)
# function to set the magnetisation
def perturbed_magnetisation(pos):
x, y, z = pos
newx = x * 1e9
newy = y * 1e9
if 8 < newx < 14 and -3 < newy < 3:
# the magnetisation is twisted a bit
import math
"""
periodic spinwaves example straight from nmag's documentation
http://nmag.soton.ac.uk/nmag/0.2/manual/html/example_periodic_spinwaves/doc.html
minus the periodic part...
"""
# define magnetic material
Py = nmag.MagMaterial(name="Py",
Ms=SI(1e6, "A/m"),
exchange_coupling=SI(13.0e-12, "J/m"),
llg_damping=SI(0.02, ""))
# create simulation object
sim = nmag.Simulation("spinwaves", do_demag=False)
# load mesh
sim.load_mesh("film.nmesh", [("film", Py)], unit_length=SI(1e-9, "m"))
# function to set the magnetisation
def perturbed_magnetisation(pos):
x, y, z = pos
newx = x * 1e9
newy = y * 1e9
if 8 < newx < 14 and -3 < newy < 3:
# the magnetisation is twisted a bit
return [
1.0, 5. * (math.cos(math.pi * ((newx - 11) / 6.)))**3 *
import nmag
from nmag import SI, every, at
from nsim.si_units import si
import math
# Create simulation object (no demag field!)
sim = nmag.Simulation(do_demag=False)
# Function to compute the scalar product of the vectors a and b
def scalar_product(a, b):
return a[0] * b[0] + a[1] * b[1] + a[2] * b[2]
# Here we define a function which returns the energy for a uniaxial
# anisotropy of order 4.
K1 = SI(43e3, "J/m^3")
K2 = SI(21e3, "J/m^3")
axis = [0, 0, 1] # The (normalised) axis
def my_anisotropy(m):
a = scalar_product(axis, m)
return -K1 * a**2 - K2 * a**4
my_material = nmag.MagMaterial(name="MyMat",
Ms=SI(1e6, "A/m"),
exchange_coupling=SI(10e-12, "J/m"),
anisotropy=my_anisotropy,
anisotropy_order=4)
# example 2 of the nmag documentation
# without demag but with external field
mat_Py = nmag.MagMaterial(name="Py",
Ms=SI(0.86e6, "A/m"),
exchange_coupling=SI(13.0e-12, "J/m"),
llg_damping=0.1)
L = 30.0e-9
H = 10.0e-9
W = 10.0e-9
def m0(r):
mx = 2 * r[0] / L - 1
my = 2 * r[1] / W - 1
mz = 1
return [mx, my, mz]
sim = nmag.Simulation("bar", do_demag=False)
sim.load_mesh("bar.nmesh.h5", [("Py", mat_Py)], unit_length=SI(1e-9, "m"))
sim.set_H_ext([1, 0, 0], SI(0.43e6, "A/m"))
sim.set_m(m0)
sim.set_params(stopping_dm_dt=1 * degrees_per_ns,
ts_rel_tol=1e-6,
ts_abs_tol=1e-6)
sim.relax(save=[('averages', every('time', SI(5e-11, "s")))])
import nmag
from nmag import SI, mesh
import nmesh
import os
H_x = SI(0.0e6, "A/m")
H_y = SI(0.0e6, "A/m")
H_z = SI(0.0e6, "A/m")
intensive_param_by_name = {"H_x": H_x, "H_y": H_y, "H_z": H_z}
mat_Py = nmag.MagMaterial(name="Py",
Ms=SI(1e6, "A/m"),
exchange_coupling=SI(13.0e-12, "J/m"))
sim = nmag.Simulation("sphere", fem_only=False)
unit_length = SI(1e-9, "m")
meshfile = "central-sphere-fine.nmesh.h5"
sim.load_mesh(meshfile, [("Py", mat_Py)], unit_length=unit_length)
def initial_magnetization((x, y, z), mag_type):
return [1, 0, 0]
sim.set_magnetization(initial_magnetization)
sim.compute_H_fields()
sim.fun_update_energies([])
from nmag import SI
import nmeshlib.unidmesher as unidmesher
L = 10
mesh_unit = SI(1e-9, "m") # mesh unit (1 nm)
layers = [(0.0, L)] # the mesh
discretization = 0.1 # discretization
# Initial magnetization
xfactor = float(SI("m") / (L * mesh_unit))
def m0(r):
return [np.cos(r[0] * np.pi * xfactor), np.sin(r[0] * np.pi * xfactor), 0]
mat_Py = nmag.MagMaterial(name="Py", Ms=SI(42, "A/m"))
sim = nmag.Simulation("Hans' configuration", do_demag=False)
mesh_file_name = '1d.nmesh'
mesh_lists = unidmesher.mesh_1d(layers, discretization)
unidmesher.write_mesh(mesh_lists, out=mesh_file_name)
sim.load_mesh(mesh_file_name, [("Py", mat_Py)], unit_length=mesh_unit)
sim.set_m(m0)
mod_dir = os.path.dirname(os.path.abspath(__file__))
np.savetxt(os.path.join(mod_dir, "nmag_exchange_energy_density.txt"),
sim.get_subfield("E_exch_Py"))
import nmag
from nmag import SI, mesh
import nmesh
import os, sys
H_x = SI(0.0e6, "A/m")
H_y = SI(0.0e6, "A/m")
H_z = SI(0.0e6, "A/m")
intensive_param_by_name = {"H_x": H_x, "H_y": H_y, "H_z": H_z}
mat_Py = nmag.MagMaterial(name="Py",
Ms=SI(1e6, "A/m"),
exchange_coupling=SI(13.0e-12, "J/m"))
sim = nmag.Simulation("sphere", fem_only=True)
unit_length = SI(1e-9, "m")
meshfile = "sphere-test-rho-phi2.nmesh"
sim.load_mesh(meshfile, [("void", []), ("Py", mat_Py)],
unit_length=unit_length)
def initial_magnetization((x, y, z), mag_type):
return [1, 0, 0]
sim.set_magnetization(initial_magnetization)
sim.compute_H_fields()
sim.fun_update_energies([])
import nmag
from nmag import SI, si
temperature = SI(2.0, "K")
ps = SI(1e-12, "s")
sim = nmag.Simulation(temperature=temperature,
user_seed_T = 0,
thermal_delta_t=0.001*ps)
# define magnetic material (data from Kronmueller)
NdFeB = nmag.MagMaterial(name="NdFeB",
Ms=1.6*si.Tesla/si.mu0,
exchange_coupling=SI(7.3e-12, "J/m"),
anisotropy=nmag.uniaxial_anisotropy(axis=[0.01,0.01,1],\
K1=SI(4.3e6, "J/m^3"),\
K2=SI(0*0.65e6, "J/m^3")))
# load mesh
sim.load_mesh("cube.nmesh.h5", [("cube", NdFeB)], unit_length=SI(1.0e-9,"m") )
# set initial magnetisation from the equilibrium configuration
# with the field = 4.92e6 A/m which has id=19 (check with 'ncol thermal-0K id H_ext_2')
magn_from_file = nmag.get_subfield_from_h5file('thermal-0K_dat.h5','m_NdFeB',id=10)
sim.set_m(magn_from_file)
# apply external field in -z direction
sim.set_H_ext([0,0,-4.92],unit=SI(1e6,'A/m'))
num_steps = 100
for n in range(0, num_steps):
