def test_zeeman_energy():
mu0 = 4 * np.pi * 1e-7
# A system of 8 cells ( not using nm units)
mesh = CuboidMesh(dx=2, dy=2, dz=2,
nx=2, ny=2, nz=2
)
sim = Sim(mesh)
Ms = 1e5
sim.set_Ms(Ms)
sim.set_m((0, 0, 1))
H = 0.1 / mu0
zeeman = Zeeman((0, 0, H))
sim.add(zeeman)
field = zeeman.compute_field()
zf = sim.get_interaction('Zeeman')
# -> ->
# Expected energy: Int ( -mu0 M * H ) dV
# Since we have 8 cells with the same M, we just sum their contrib
exp_energy = 8 * (-mu0 * H * Ms * mesh.dx * mesh.dy * mesh.dz)
assert np.abs(zf.compute_energy() - exp_energy) < 1e-10
def test_add_remove_interaction_simple():
mesh = CuboidMesh(nx=10, ny=10, nz=10, unit_length=1e-9)
name = 'test_add_remove_intn_simple'
sim = Sim(mesh, name=name)
sim.set_m(lambda pos: (0, 0, 1))
sim.set_Ms(5.8e5)
exch = UniformExchange(A=1e-11, name='Exchange')
zee = Zeeman((0, 0, 0.05 / constant.mu_0), name='Zeeman')
sim.add(exch)
sim.add(zee)
sim.driver.run_until(1e-9)
sim.remove('Zeeman')
sim.driver.run_until(2e-9)
f = open(name + '.txt')
lines = f.read().split('\n')
headers = lines[0].split()
first_data = lines[2].split()
last_data = lines[2].split()
# Find the position in the data table
position = headers.index('E_Zeeman')
assert np.abs(float(last_data[position])) < 1e-15
dy=dy,
dz=dz,
x0=-Lx / 2,
y0=-Ly / 2,
z0=-Lz / 2,
unit_length=1e-9)
sim = Sim(mesh)
Ms = 1.1e6
A = 2e-12
D = 3.9e-3
Ku = 2.5e6
Bz = 1.
sim.set_Ms(Ms)
sim.add(fidimag.micro.UniformExchange(A))
sim.add(fidimag.micro.UniaxialAnisotropy(Ku, axis=(0, 0, 1)))
sim.add(fidimag.micro.Zeeman((0, 0, Bz / C.mu_0)))
# sim.add(fidimag.micro.DMI(D, dmi_type='interfacial'))
# For a C_n material, there is a kind of instability when one of the DM
# constants is larger than approx 0.7 times the other DM constant
sim.add(fidimag.micro.DMI([D, 0.6 * D], dmi_type='C_n'))
sim.set_m(init_m)
sim.driver.do_precession = False
sim.driver.alpha = 0.9
