def test_script(self):
system = mc.System(name="test_system")
system.hamiltonian += mc.Exchange(1e-12)
system.hamiltonian += mc.Demag()
system.hamiltonian += mc.UniaxialAnisotropy(1e3, (0, 1, 0))
system.hamiltonian += mc.Zeeman((0, 1e6, 0))
system.dynamics += mc.Precession(2.211e5)
system.dynamics += mc.Damping(0.1)
mesh = mc.Mesh((0, 0, 0), (5, 5, 5), (1, 1, 1))
system.m = df.Field(mesh, dim=3, value=(0, 1, 0), norm=1)
script = system._script
assert script[-1] == "\n"
assert "mu0mm" in script
assert "SetGridSize(5, 5, 5)" in script
assert "SetCellSize(1, 1, 1)" in script
assert "Aex=1e-12" in script
assert "enabledemag=true" in script
assert "B_ext=vector(0*mu0mm,1000000.0*mu0mm,0*mu0mm)" in script
assert "Ku1=1000.0" in script
assert "Ku2=0" in script
assert "anisu=vector(0,1,0)" in script
return None
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 / mc.mu0) # magnetisation saturation (A/m)
A = 0.5 * mc.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 = mc.Mesh(p1=(0, 0, 0),
p2=(cubesize, cubesize, cubesize),
cell=(cellsize, cellsize, cellsize))
# Remove any previous simulation directories.
if os.path.exists(name):
shutil.rmtree(name)
system = mc.System(name=name)
system.hamiltonian = mc.Exchange(A) + mc.UniaxialAnisotropy(K, u) + \
mc.Demag()
system.m = df.Field(mesh, value=m_init, norm=Ms)
md = mc.RelaxDriver()
md.drive(system)
if os.path.exists(name):
shutil.rmtree(name)
return system
def test_script(self):
for K1, K2, u in self.valid_args:
anisotropy = mc.UniaxialAnisotropy(K1=K1, K2=K2, u=u)
script = anisotropy._script
assert script[0:2] == "//"
assert script[-1] == "\n"
lines = script.split("\n")
assert lines[0] == "// UniaxialAnisotropy"
assert lines[1] == "Ku1={}".format(K1)
assert lines[2] == "Ku2={}".format(K2)
assert lines[3] == "anisu=vector({},{},{})".format(*u)
assert script.count("\n") == 5
assert len(lines) == 6
def test_skyrmion():
name = "skyrmion"
# Remove any previous simulation directories.
if os.path.exists(name):
shutil.rmtree(name)
mesh = mc.Mesh(p1=(-50e-9, -50e-9, 0),
p2=(50e-9, 50e-9, 10e-9),
cell=(5e-9, 5e-9, 5e-9))
system = mc.System(name="skyrmion")
system.hamiltonian = mc.Exchange(A=1.6e-11) + \
mc.DMI(D=4e-3, crystalclass="cnv") + \
mc.UniaxialAnisotropy(K1=0.51e6, K2=0.1, u=(0, 0, 1)) + \
mc.Demag() + \
mc.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 = mc.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_total_energy(self):
system = mc.System(name="test_system")
system.hamiltonian += mc.Exchange(1e-12)
system.hamiltonian += mc.UniaxialAnisotropy(1e3, (0, 1, 0))
system.hamiltonian += mc.Zeeman((0, 1e6, 0))
system.dynamics += mc.Precession(2.211e5)
system.dynamics += mc.Damping(0.1)
mesh = mc.Mesh((0, 0, 0), (5, 5, 5), (1, 1, 1))
system.m = df.Field(mesh, dim=3, value=(0, 1, 0), norm=1)
with pytest.raises(AttributeError):
system.total_energy()
return None