def minimise_system_energy(L, m_init):
N = 16 # discretisation in one dimension
cubesize = 100e-9 # cube edge length (m)
cellsize = cubesize / N # discretisation in all three dimensions.
lex = cubesize / L # exchange length.
Km = 1e6 # magnetostatic energy density (J/m**3)
Ms = np.sqrt(2 * Km / oc.mu0) # magnetisation saturation (A/m)
A = 0.5 * oc.mu0 * Ms**2 * lex**2 # exchange energy constant
K = 0.1 * Km # Uniaxial anisotropy constant
u = (0, 0, 1) # Uniaxial anisotropy easy-axis
p1 = (0, 0, 0) # Minimum sample coordinate.
p2 = (cubesize, cubesize, cubesize) # Maximum sample coordinate.
cell = (cellsize, cellsize, cellsize) # Discretisation.
mesh = oc.Mesh(p1=(0, 0, 0),
p2=(cubesize, cubesize, cubesize),
cell=(cellsize, cellsize, cellsize))
system = oc.System(name=name)
system.hamiltonian = oc.Exchange(A) + oc.UniaxialAnisotropy(K, u) + \
oc.Demag()
system.m = df.Field(mesh, value=m_init, norm=Ms)
md = oc.MinDriver()
md.drive(system)
return system
def test_relax_with_cubicanisotropy():
name = "cubic_anisotropy"
L = 100e-9
d = 5e-9
Ms = 8e6
# Remove any previous simulation directories.
if os.path.exists(name):
shutil.rmtree(name)
system = oc.System(name=name)
system.hamiltonian = oc.CubicAnisotropy(K1=5e6, u1=(1, 0, 0), u2=(0, 1, 0))
mesh = oc.Mesh(p1=(0, 0, 0), p2=(L, L, L), cell=(d, d, d))
def m_init(pos):
x, y, z = pos
if x < 30e-9:
return (0.7, 0.1, 0.3)
elif x > 70e-9:
return (0.1, 0.7, 0.3)
else:
return (0.3, 0.1, 0.7)
system.m = df.Field(mesh, value=m_init, norm=Ms)
md = oc.MinDriver()
md.drive(system)
comp_value = 0.99 * Ms
assert system.m((10e-9, 0, 0))[0] > comp_value
assert system.m((50e-9, 0, 0))[2] > comp_value
assert system.m((80e-9, 0, 0))[1] > comp_value
shutil.rmtree(name)
def __init__(self,
A=20e-12,
Ms=0.648,
B=0.1,
L=400e-9,
thickness=100e-9,
init_state_radius=80e-9,
cell=(4e-9, 4e-9, 4e-9)):
self.A = A
self.Ms = Ms / mu0
self.Ku = A / 2.3e-16
self.B = B
self.L = L
self.thickness = thickness
print('Exch length lex = ',
1e9 * np.sqrt(2 * self.A / (mu0 * self.Ms**2)), 'nm')
self.mesh = oc.Mesh(p1=(-self.L / 2, -self.L / 2, -self.thickness / 2),
p2=(self.L / 2, self.L / 2, self.thickness / 2),
cell=cell)
self.system = oc.System(name='oommf_typeII_bubble')
# Add interactions
self.system.hamiltonian = (
oc.Exchange(A=self.A) +
oc.UniaxialAnisotropy(K1=self.Ku, u=(0, 0, 1)) + oc.Demag() +
oc.Zeeman((0, 0, self.B / mu0)))
self.system.m = df.Field(
self.mesh,
value=lambda r: init_type2bubble_bls_II(r, init_state_radius),
norm=self.Ms)
# self.system.m = df.Field(self.mesh, value=(0, 0.1, 0.99),
# norm=self.Ms)
self.md = oc.MinDriver()
# Get system cordinates
self.coordinates = np.array(list(self.system.m.mesh.coordinates))
# Turn coordinates into a (N, 3) array and save in corresponding
# variables scaled in nm
self.x, self.y, self.z = (self.coordinates[:, 0] * 1e9,
self.coordinates[:, 1] * 1e9,
self.coordinates[:, 2] * 1e9)
# Array with uniue z coordinates
self.xs = np.unique(self.x)
self.ys = np.unique(self.y)
self.zs = np.unique(self.z)
self.z_layers = {}
for i, z in enumerate(self.zs):
self.z_layers[i] = '{:.2f} nm'.format(z)
# Compute the initial magnetisation profile
self.compute_magnetisation()
def test_choose_runner():
system = mm.examples.macrospin()
md = oc.MinDriver()
runner = oc.oommf.TclOOMMFRunner(
oommf_tcl=os.environ.get('OOMMFTCL', None))
md.drive(system, runner=runner)
runner = oc.oommf.ExeOOMMFRunner(oommf_exe='oommf')
md.drive(system, runner=runner)
def test_save_mif(self):
md = oc.MinDriver()
md._makedir(self.system)
md._save_mif(self.system)
miffilename = os.path.join("tds", "tds.mif")
assert os.path.isfile(miffilename)
lines = open(miffilename, "r").readlines()
assert lines[0] == "# MIF 2.1\n"
assert lines[-1][-1] == "1"
shutil.rmtree("tds")
def test_stdprob5():
name = "stdprob5"
# Remove any previous simulation directories.
if os.path.exists(name):
shutil.rmtree(name)
# Geometry
lx = 100e-9 # x dimension of the sample(m)
ly = 100e-9 # y dimension of the sample (m)
lz = 10e-9 # sample thickness (m)
# Material (permalloy) parameters
Ms = 8e5 # saturation magnetisation (A/m)
A = 1.3e-11 # exchange energy constant (J/m)
# Dynamics (LLG + STT equation) parameters
gamma = 2.211e5 # gyromagnetic ratio (m/As)
alpha = 0.1 # Gilbert damping
ux = -72.35 # velocity in x direction
beta = 0.05 # non-adiabatic STT parameter
system = oc.System(name=name)
mesh = oc.Mesh(p1=(0, 0, 0),
p2=(100e-9, 100e-9, 10e-9),
cell=(5e-9, 5e-9, 5e-9))
system.mesh = mesh
system.hamiltonian = oc.Exchange(A) + oc.Demag()
def m_vortex(pos):
x, y, z = pos[0] / 1e-9 - 50, pos[1] / 1e-9 - 50, pos[2] / 1e-9
return (-y, x, 10)
system.m = df.Field(mesh, value=m_vortex, normalisedto=Ms)
md = oc.MinDriver()
md.drive(system)
system.dynamics += oc.Precession(gamma) + oc.Damping(alpha) + \
oc.STT(u=(ux, 0, 0), beta=beta)
td = oc.TimeDriver()
td.drive(system, t=8e-9, n=100)
mx = system.dt["mx"].as_matrix()
assert -0.03 < mx.max() < 0
assert -0.35 < mx.min() < -0.30
shutil.rmtree(name)
def test_skyrmion():
name = "skyrmion"
# Remove any previous simulation directories.
if os.path.exists(name):
shutil.rmtree(name)
mesh = oc.Mesh(p1=(-50e-9, -50e-9, 0),
p2=(50e-9, 50e-9, 10e-9),
cell=(5e-9, 5e-9, 5e-9))
system = oc.System(name="skyrmion")
system.hamiltonian = oc.Exchange(A=1.6e-11) + \
oc.DMI(D=4e-3, kind="interfacial") + \
oc.UniaxialAnisotropy(K1=0.51e6, K2=0.1, u=(0, 0, 1)) + \
oc.Demag() + \
oc.Zeeman(H=(0, 0, 2e5))
Ms = 1.1e6
def Ms_fun(pos):
x, y, z = pos
if (x**2 + y**2)**0.5 < 50e-9:
return Ms
else:
return 0
def m_init(pos):
x, y, z = pos
if (x**2 + y**2)**0.5 < 10e-9:
return (0, 0.1, -1)
else:
return (0, 0.1, 1)
system.m = df.Field(mesh, value=m_init, norm=Ms_fun)
md = oc.MinDriver()
md.drive(system)
# Check the magnetisation at the sample centre.
assert system.m((0, 0, 0))[2] / Ms < -0.97
# Check the magnetisation at the sample edge.
assert system.m((50e-9, 0, 0))[2] / Ms > 0
shutil.rmtree(name)
def test_script(self):
md = oc.MinDriver()
script = md._script(self.system)
assert script[0] == "#"
assert script[-1] == "1"
assert script.count("#") == 5
assert script.count("Specify") == 3
assert script.count("Destination") == 2
assert script.count("Schedule") == 2
assert script.count("mmArchive") == 2
assert script.count("Stage") == 2
assert "Oxs_CGEvolve" in script
assert "Oxs_MinDriver" in script
assert "Oxs_FileVectorField" in script
def test_stdprobfmr():
name = "stdprobfmr"
# Remove any previous simulation directories.
if os.path.exists(name):
shutil.rmtree(name)
lx = ly = 120e-9 # x and y dimensions of the sample(m)
lz = 10e-9 # sample thickness (m)
dx = dy = dz = 10e-9 # discretisation in x, y, and z directions (m)
Ms = 8e5 # saturation magnetisation (A/m)
A = 1.3e-11 # exchange energy constant (J/m)
H = 8e4 * np.array([0.81345856316858023, 0.58162287266553481, 0.0])
alpha = 0.008 # Gilbert damping
gamma = 2.211e5
mesh = oc.Mesh(p1=(0, 0, 0), p2=(lx, ly, lz), cell=(dx, dy, dz))
system = oc.System(name="stdprobfmr")
system.hamiltonian = oc.Exchange(A) + oc.Demag() + oc.Zeeman(H)
system.dynamics = oc.Precession(gamma) + oc.Damping(alpha)
system.m = df.Field(mesh, value=(0, 0, 1), norm=Ms)
md = oc.MinDriver()
md.drive(system)
H = 8e4 * np.array([0.81923192051904048, 0.57346234436332832, 0.0])
system.hamiltonian.zeeman.H = H
T = 20e-9
n = 4000
td = oc.TimeDriver()
td.drive(system, t=T, n=n)
t = system.dt['t'].as_matrix()
my = system.dt['mx'].as_matrix()
psd = np.log10(np.abs(scipy.fftpack.fft(my))**2)
f_axis = scipy.fftpack.fftfreq(4000, d=20e-9/4000)
shutil.rmtree(name)
def test_drive(self):
md = oc.MinDriver()
md.drive(self.system)
dirname = os.path.join("tds", "")
assert os.path.exists(dirname)
miffilename = os.path.join("tds", "tds.mif")
assert os.path.isfile(miffilename)
omf_files = list(glob.iglob("tds/*.omf"))
odt_files = list(glob.iglob("tds/*.odt"))
assert len(omf_files) == 2
omffilename = os.path.join("tds", "m0.omf")
assert omffilename in omf_files
assert len(odt_files) == 1
shutil.rmtree("tds")
def test_script(self):
md = oc.MinDriver()
script = md.script(self.system)
assert script[0] == "#"
assert script[-1] == "1"
assert script.count("#") == 3
assert script.count("Specify") == 2
assert script.count("Destination") == 2
assert script.count("Schedule") == 2
assert script.count("mmArchive") == 2
assert script.count("Stage") == 2
assert "Oxs_CGEvolve" in script
assert "Oxs_MinDriver" in script
assert "Oxs_FileVectorField" in script
lines = script.split("\n")
assert lines[8] == " Ms {}".format(8e5)
assert lines[13] == " file m0.omf"
assert lines[16] == " basename tds"
def test_silent(capsys):
md = oc.MinDriver()
md.drive(mm.examples.macrospin())
captured = capsys.readouterr()
assert "Running OOMMF" in captured.out
assert captured.err == ""
md.drive(mm.examples.macrospin(), verbose=2)
captured = capsys.readouterr()
assert "Running OOMMF" in captured.out
assert captured.err == ""
td = oc.TimeDriver()
td.drive(mm.examples.macrospin(), t=1e-10, n=10, verbose=2)
captured = capsys.readouterr()
assert captured.out == ""
assert "files written" in captured.err # tqdm output on stderr
md.drive(mm.examples.macrospin(), verbose=0)
captured = capsys.readouterr()
assert captured.out == ""
assert captured.err == ""
shutil.rmtree(name) L = 30e-9 # (m) cellsize = (10e-9, 15e-9, 5e-9) # (m) mesh = oc.Mesh((0, 0, 0), (L, L, L), cellsize) system = oc.System(name=name) A = 1.3e-11 # (J/m) H = (1e6, 0.0, 2e5) system.hamiltonian = oc.Exchange(A=A) + oc.Zeeman(H=H) gamma = 2.211e5 # (m/As) alpha = 0.02 system.dynamics = oc.Precession(gamma) + oc.Damping(alpha) Ms = 8e5 # (A/m) system.m = df.Field(mesh, value=(0.0, 0.25, 0.1), norm=Ms) td = oc.TimeDriver() td.drive(system, t=25e-12, n=25) # updates system.m in-place td.drive(system, t=15e-12, n=15) td.drive(system, t=5e-12, n=10) md = oc.MinDriver() md.drive(system) system.hamiltonian.zeeman.H = (0.0, 0.0, 1.0e6) td.drive(system, t=5e-12, n=5) md.drive(system)
def test_stdprob4():
name = "stdprob4"
# Remove any previous simulation directories.
if os.path.exists(name):
shutil.rmtree(name)
L, d, th = 500e-9, 125e-9, 3e-9 # (m)
cellsize = (5e-9, 5e-9, 3e-9) # (m)
mesh = oc.Mesh((0, 0, 0), (L, d, th), cellsize)
system = oc.System(name=name)
A = 1.3e-11 # (J/m)
system.hamiltonian = oc.Exchange(A) + oc.Demag()
gamma = 2.211e5 # (m/As)
alpha = 0.02
system.dynamics = oc.Precession(gamma) + oc.Damping(alpha)
Ms = 8e5 # (A/m)
system.m = df.Field(mesh, value=(1, 0.25, 0.1), norm=Ms)
md = oc.MinDriver()
md.drive(system) # updates system.m in-place
dirname = os.path.join(name, "")
miffilename = os.path.join(name, "{}.mif".format(name))
assert os.path.exists(dirname)
assert os.path.isfile(miffilename)
omf_files = list(glob.iglob("{}/*.omf".format(name)))
odt_files = list(glob.iglob("{}/*.odt".format(name)))
assert len(omf_files) == 2
omffilename = os.path.join(name, "m0.omf")
assert omffilename in omf_files
assert len(odt_files) == 1
shutil.rmtree(name)
H = (-24.6e-3/oc.mu0, 4.3e-3/oc.mu0, 0)
system.hamiltonian += oc.Zeeman(H)
td = oc.TimeDriver()
td.drive(system, t=1e-9, n=200)
dirname = os.path.join(name, "")
miffilename = os.path.join(name, "{}.mif".format(name))
assert os.path.exists(dirname)
assert os.path.isfile(miffilename)
omf_files = list(glob.iglob("{}/*.omf".format(name)))
odt_files = list(glob.iglob("{}/*.odt".format(name)))
assert len(omf_files) == 201
omffilename = os.path.join(name, "m0.omf")
assert omffilename in omf_files
assert len(odt_files) == 1
myplot = system.dt.plot("t", "my")
figfilename = os.path.join(name, "stdprob4-t-my.pdf")
myplot.figure.savefig(figfilename)
assert os.path.isfile(figfilename)
t = system.dt["t"].as_matrix()
my = system.dt["my"].as_matrix()
assert abs(min(t) - 5e-12) < 1e-20
assert abs(max(t) - 1e-9) < 1e-20
# Eye-norm test.
assert 0.7 < max(my) < 0.8
assert -0.5 < min(my) < -0.4
shutil.rmtree(name)
def test_choose_runner():
system = mm.examples.macrospin()
md = oc.MinDriver()
runner = oc.oommf.ExeOOMMFRunner()
md.drive(system, runner=runner)
region = df.Region(p1=p1, p2=p2)
mesh = df.Mesh(region=region, cell=cell)
Ms = 8e5
A = 1.3e-11
H = (1e6, 0.0, 2e5)
alpha = 0.02
system = mm.System(name=name)
system.energy = mm.Exchange(A=A) + mm.Zeeman(H=H)
system.dynamics = mm.Precession(gamma0=mm.consts.gamma0) + mm.Damping(
alpha=alpha)
system.m = df.Field(mesh, dim=3, value=(0.0, 0.25, 0.1), norm=Ms)
td = mc.TimeDriver()
td.drive(system, t=25e-12, n=25, dirname=dirname) # drive-0
td.drive(system, t=15e-12, n=15, dirname=dirname) # drive-1
td.drive(system, t=5e-12, n=10, dirname=dirname) # drive-2
md = mc.MinDriver()
md.drive(system, dirname=dirname) # drive-3
system.energy.zeeman.H = (0.0, 0.0, 1.0e6)
td.drive(system, t=5e-12, n=5, dirname=dirname) # drive-4
md.drive(system, dirname=dirname, output_step=True) # drive-5
hd = mc.HysteresisDriver()
hd.drive(system, Hmin=(0, 0, 1e6), Hmax=(0, 0, -1e6), n=21,
dirname=dirname) # drive-6
