def relax_system(mesh, Dx=0.005, Dp=0.01):
mat = UnitMaterial()
sim = Sim(mesh, name='test_energy')
sim.set_tols(rtol=1e-10, atol=1e-12)
sim.alpha = mat.alpha
sim.gamma = mat.gamma
sim.pins = pin_fun
exch = UniformExchange(mat.J)
sim.add(exch)
anis = Anisotropy(Dx, axis=[1, 0, 0], name='Dx')
sim.add(anis)
anis2 = Anisotropy([0, 0, -Dp], name='Dp')
sim.add(anis2)
sim.set_m((1, 1, 1))
T = 100
ts = np.linspace(0, T, 201)
for t in ts:
# sim.save_vtk()
sim.run_until(t)
# sim.save_vtk()
np.save('m0.npy', sim.spin)
def test_skx_num():
mesh = CuboidMesh(nx=120, ny=120, nz=1, periodicity=(True, True, False))
sim = Sim(mesh, name='skx_num')
sim.set_tols(rtol=1e-6, atol=1e-6)
sim.alpha = 1.0
sim.gamma = 1.0
sim.mu_s = 1.0
sim.set_m(init_m)
sim.do_procession = False
J = 1.0
exch = UniformExchange(J)
sim.add(exch)
D = 0.09
dmi = DMI(D)
sim.add(dmi)
zeeman = Zeeman([0, 0, 5e-3])
sim.add(zeeman)
sim.relax(dt=2.0, stopping_dmdt=1e-2, max_steps=1000,
save_m_steps=None, save_vtk_steps=None)
skn = sim.skyrmion_number()
print 'skx_number', skn
assert skn > -1 and skn < -0.99
def relax_system(mesh, Dx=0.005, Dp=0.01):
mat = UnitMaterial()
sim = Sim(mesh, name='test_energy')
print('Created sim')
sim.set_tols(rtol=1e-10, atol=1e-12)
sim.alpha = mat.alpha
sim.gamma = mat.gamma
sim.pins = pin_fun
exch = UniformExchange(mat.J)
sim.add(exch)
print('Added UniformExchange')
anis = Anisotropy(Dx, axis=[1, 0, 0], name='Dx')
sim.add(anis)
print('Added Anisotropy')
anis2 = Anisotropy([0, 0, -Dp], name='Dp')
sim.add(anis2)
print('Added Anisotropy 2')
sim.set_m((1, 1, 1))
T = 100
ts = np.linspace(0, T, 201)
for t in ts:
# sim.save_vtk()
sim.run_until(t)
print('Running -', t)
# sim.save_vtk()
np.save('m0.npy', sim.spin)
def test_skx_num():
mesh = CuboidMesh(nx=120, ny=120, nz=1, periodicity=(True, True, False))
sim = Sim(mesh, name='skx_num')
sim.set_tols(rtol=1e-6, atol=1e-6)
sim.alpha = 1.0
sim.gamma = 1.0
sim.mu_s = 1.0
sim.set_m(init_m)
sim.do_procession = False
J = 1.0
exch = UniformExchange(J)
sim.add(exch)
D = 0.09
dmi = DMI(D)
sim.add(dmi)
zeeman = Zeeman([0, 0, 5e-3])
sim.add(zeeman)
sim.relax(dt=2.0,
stopping_dmdt=1e-2,
max_steps=1000,
save_m_steps=None,
save_vtk_steps=None)
skn = sim.skyrmion_number()
print 'skx_number', skn
assert skn > -1 and skn < -0.99
def test_skx_num_atomistic():
"""
Test the *finite spin chirality* or skyrmion number for
a discrete spins simulation in a two dimensional lattice
The expression is (PRL 108, 017601 (2012)) :
Q = S_i \dot ( S_{i+1} X S_{j+1} )
+ S_i \dot ( S_{i-1} X S_{j-1} )
which measures the chirality taking two triangles of spins
per lattice site i:
S_{i} , S_{i + x} , S_{i + y} and
S_{i} , S_{i - x} , S_{i - y}
The area of the two triangles cover a unit cell, thus the sum
cover the whole area of the atomic lattice
This test generate a skyrmion pointing down with unrealistic
paremeters.
"""
mesh = CuboidMesh(nx=120, ny=120, nz=1,
periodicity=(True, True, False))
sim = Sim(mesh, name='skx_num')
sim.set_tols(rtol=1e-6, atol=1e-6)
sim.alpha = 1.0
sim.gamma = 1.0
sim.mu_s = 1.0
sim.set_m(lambda pos: init_m(pos, 60, 60, 20))
sim.do_precession = False
J = 1.0
exch = UniformExchange(J)
sim.add(exch)
D = 0.09
dmi = DMI(D)
sim.add(dmi)
zeeman = Zeeman([0, 0, 5e-3])
sim.add(zeeman)
sim.relax(dt=2.0, stopping_dmdt=1e-2, max_steps=1000,
save_m_steps=None, save_vtk_steps=None)
skn = sim.skyrmion_number()
print('skx_number', skn)
assert skn > -1 and skn < -0.99
from fidimag.atomistic import Sim from fidimag.common.cuboid_mesh import CuboidMesh from fidimag.atomistic import UniformExchange, Zeeman import fidimag.common.constant as const mesh = CuboidMesh(nx=1, ny=1, dx=1, dy=1) sim = Sim(mesh, name='relax_sk') sim.gamma = const.gamma sim.set_m((1, 0, 0)) sim.add(Zeeman((0, 0, 25.))) sim.run_until(1e-11) sim.set_tols(rtol=1e-10, atol=1e-12) sim.run_until(2e-11)
tenergy.set_text('Energy: {:.6e} J'.format(sim.compute_energy()))
# fig.show()
fig.canvas.draw()
sim.save_vtk()
else:
# print(np.min(sim.mesh.coordinates[:, 1]), np.max(sim.mesh.coordinates[:, 1]))
if args.save_initial_vtk:
sim.save_vtk()
# Fidimag automatically saves the last state (?)
sim.driver.do_precession = False
if args.tols:
sim.set_tols(rtol=args.tols[0], atol=args.tols[1])
if args.driver == 'llg':
sim.driver.relax(dt=1e-13, stopping_dmdt=args.stopping_dmdt,
max_steps=args.max_steps,
save_m_steps=args.save_files,
save_vtk_steps=args.save_files)
# Set OpenMP for the integrator
sim.driver.set_integrator('sundials_openmp', use_jac=False)
elif args.driver == 'minimiser':
sim.driver.minimise(max_steps=args.max_steps,
stopping_dm=args.stopping_dmdt,
save_data_steps=1000)
from fidimag.atomistic import Sim from fidimag.common.cuboid_mesh import CuboidMesh from fidimag.atomistic import UniformExchange, Zeeman from fidimag.atomistic import Constant # Import physical constants from fidimag const = Constant() mesh = CuboidMesh(nx=1, ny=1, dx=1, dy=1) sim = Sim(mesh, name='relax_sk') sim.gamma = const.gamma sim.set_m((1, 0, 0)) sim.add(Zeeman((0, 0, 25.))) sim.run_until(1e-11) sim.set_tols(rtol=1e-10, atol=1e-12) sim.run_until(2e-11)
