def test_exch_field_oommf(A=1e-11, Ms=2.6e5): mesh = CuboidMesh(nx=10, ny=3, nz=2, dx=0.5, unit_length=1e-9) sim = Sim(mesh) sim.Ms = Ms exch = UniformExchange(A=A) sim.add(exch) def init_m(pos): x, y, z = pos return (np.sin(x) + y + 2.3 * z, np.cos(x) + y + 1.3 * z, 0) sim.set_m(init_m) field = exch.compute_field() init_m0 = """ return [list [expr {sin($x*1e9)+$y*1e9+$z*2.3e9}] [expr {cos($x*1e9)+$y*1e9+$z*1.3e9}] 0] """ omf_file = os.path.join(os.path.dirname(os.path.abspath(__file__)), 'omfs', 'test_exch_field_oommf.ohf' ) ovf = OMF2(omf_file) field_oommf = ovf.get_all_mags() #field_oommf = compute_exch_field(mesh, Ms=Ms, init_m0=init_m0, A=A) mx0, mx1, mx2 = compare_fields(field_oommf, field) assert max([mx0, mx1, mx2]) < 1e-12
def test_dmi_field_oommf(D=4.1e-3, Ms=2.6e5): mesh = CuboidMesh(nx=10, ny=3, nz=2, dx=0.5, unit_length=1e-9) sim = Sim(mesh) sim.Ms = Ms dmi = DMI(D=D, dmi_type='interfacial') sim.add(dmi) def init_m(pos): x, y, z = pos return (np.sin(x) + y + 2.3 * z, np.cos(x) + y + 1.3 * z, 0) sim.set_m(init_m) field = dmi.compute_field() init_m0 = """ return [list [expr {sin($x*1e9)+$y*1e9+$z*2.3e9}] [expr {cos($x*1e9)+$y*1e9+$z*1.3e9}] 0] """ # TODO: check the sign of DMI in OOMMF. #field_oommf = compute_dmi_field(mesh, Ms=Ms, init_m0=init_m0, D=-D) omf_file = os.path.join(os.path.dirname(os.path.abspath(__file__)),'omfs','test_dmi_field_oommf.ohf') ovf = OMF2(omf_file) field_oommf = ovf.get_all_mags() mx0, mx1, mx2 = compare_fields(field_oommf, field) assert max([mx0, mx1, mx2]) < 1e-12
def compute_field(): mesh = CuboidMesh(nx=1, ny=1, nz=1, dx=2.0, dy=2.0, dz=2.0, unit_length=1e-9, periodicity=(True, True, False)) sim = Sim(mesh, name='relax') sim.set_tols(rtol=1e-10, atol=1e-14) sim.alpha = 0.5 sim.gamma = 2.211e5 sim.Ms = 8.6e5 sim.do_precession = False sim.set_m((0,0,1)) # sim.set_m(np.load('m0.npy')) A = 1.3e-11 exch = UniformExchange(A=A) sim.add(exch) demag = Demag(pbc_2d=True) sim.add(demag) field=demag.compute_field() print field np.save('m0.npy', sim.spin)
def test_dmi_field_oommf(D=4.1e-3, Ms=2.6e5): mesh = CuboidMesh(nx=10, ny=3, nz=2, dx=0.5, unit_length=1e-9) sim = Sim(mesh) sim.Ms = Ms dmi = DMI(D=D, type='interfacial') sim.add(dmi) def init_m(pos): x, y, z = pos return (np.sin(x) + y + 2.3 * z, np.cos(x) + y + 1.3 * z, 0) sim.set_m(init_m) field = dmi.compute_field() init_m0 = (r'return [list [expr {sin($x * 1e9) + $y * 1e9 + $z * 2.3e9}] ' + r' [expr {cos($x * 1e9) + $y * 1e9 + $z * 1.3e9}] ' + r'0 ' + r'] ') # TODO: check the sign of DMI in OOMMF. field_oommf = compute_dmi_field(mesh, Ms=Ms, init_m0=init_m0, D=-D) mx0, mx1, mx2 = compare_fields(field_oommf, field) assert max([mx0, mx1, mx2]) < 1e-12
def test_energy_dmi(Ms=8e5, D=1.32e-3): mesh = CuboidMesh(nx=40, ny=50, nz=1, dx=2.5, dy=2.5, dz=3, unit_length=1e-9) sim = Sim(mesh) sim.Ms = Ms dmi = DMI(D=D, type='interfacial') #dmi = DMI(D=D, type='bulk') sim.add(dmi) def init_m(pos): x, y, z = pos return (np.sin(x) + y + 2.3 * z, np.cos(x) + y + 1.3 * z, 1) sim.set_m(init_m) dmi_energy = dmi.compute_energy() # init_m0=""" # return [list [expr {sin($x*1e9)+$y*1e9+$z*2.3e9}] [expr {cos($x*1e9)+$y*1e9+$z*1.3e9}] 1] #""" #field_oommf = compute_dmi_field(mesh, Ms=Ms, init_m0=init_m0, D=D) dmi_energy_oommf = -4.5665527749090378e-20 print 'dmi energy', dmi_energy assert abs(dmi_energy - dmi_energy_oommf) / dmi_energy_oommf < 1e-15
def relax_system(mesh): # Only relaxation sim = Sim(mesh, name='relax') # Simulation parameters sim.driver.set_tols(rtol=1e-8, atol=1e-10) sim.driver.alpha = 0.5 sim.driver.gamma = 2.211e5 sim.Ms = 8.6e5 sim.do_precession = False # The initial state passed as a function sim.set_m(init_m) # sim.set_m(np.load('m0.npy')) # Energies A = 1.3e-11 exch = UniformExchange(A=A) sim.add(exch) anis = UniaxialAnisotropy(5e4) sim.add(anis) # Start relaxation and save the state in m0.npy sim.relax(dt=1e-14, stopping_dmdt=0.00001, max_steps=5000, save_m_steps=None, save_vtk_steps=None) np.save('m0.npy', sim.spin)
def test_exch_field_oommf(A=1e-11, Ms=2.6e5): """ Compare the exchange field from Fidimag with an equivalent OOMMF simulation. OOMMF field data is taken from an OVF file. """ mesh = CuboidMesh(nx=10, ny=3, nz=2, dx=0.5, unit_length=1e-9) sim = Sim(mesh) sim.Ms = Ms exch = UniformExchange(A=A) sim.add(exch) def init_m(pos): x, y, z = pos return (np.sin(x) + y + 2.3 * z, np.cos(x) + y + 1.3 * z, 0) sim.set_m(init_m) field = exch.compute_field() # An equivalent initial magnetisation for OOMMF # The spatial variables are rescale since they are in nm init_m0 = (r'return [list [expr {sin($x * 1e9) + $y * 1e9 + $z * 2.3e9}] ' + r' [expr {cos($x * 1e9) + $y * 1e9 + $z * 1.3e9}] ' + r'0 ' + r'] ') field_oommf = compute_exch_field(mesh, Ms=Ms, init_m0=init_m0, A=A) mx0, mx1, mx2 = compare_fields(field_oommf, field) # Test if the maximum relative errors between both simulations # is small enough, for every field component assert max([mx0, mx1, mx2]) < 1e-12
def setup_simulation(mesh, m0, simulation_name, integrator="sundials", use_jac=False): sim = Sim(mesh, name=simulation_name, integrator=integrator, use_jac) sim.set_m(m0) sim.Ms = Ms sim.alpha = alpha sim.gamma = gamma sim.add(UniformExchange(A)) sim.add(Demag()) return sim
def test_with_oommf_spatial_Ms(A=1e-11): def spatial_Ms(pos): x, y = pos[0], pos[1] if x ** 2 + y ** 2 < 5 ** 2: return 2e4 else: return 0 init_m0 = (r'return [list [expr {sin($x * 1e9) + $y * 1e9 + $z * 2.3e9}] ' + r' [expr {cos($x * 1e9) + $y * 1e9 + $z * 1.3e9}] ' + r'0 ' + r'] ') init_Ms = """ if { ($x * $x + $y * $y) < 5e-9 * 5e-9 } { return 2e4 } else { return 0 } """ mesh = CuboidMesh(nx=12, ny=10, nz=2, dx=0.5, unit_length=1e-9) sim = Sim(mesh) sim.Ms = spatial_Ms def init_m(pos): x, y, z = pos return (np.sin(x) + y + 2.3 * z, np.cos(x) + y + 1.3 * z, 0) sim.set_m(init_m) exch = UniformExchange(A=A) sim.add(exch) demag = Demag() sim.add(demag) field = exch.compute_field() field_oommf = compute_exch_field( mesh, init_m0=init_m0, A=A, spatial_Ms=init_Ms) mx0, mx1, mx2 = compare_fields(field_oommf, field) assert max([mx0, mx1, mx2]) < 1e-12 field = demag.compute_field() field_oommf = compute_demag_field( mesh, spatial_Ms=init_Ms, init_m0=init_m0) mx0, mx1, mx2 = compare_fields(field_oommf, field) assert max([mx0, mx1, mx2]) < 1e-11
def test_sim_single_spin(do_plot=False): mesh = CuboidMesh(nx=1, ny=1, nz=1) sim = Sim(mesh, name='spin') alpha = 0.1 gamma = 2.21e5 sim.alpha = alpha sim.gamma = gamma sim.mu_s = 1.0 sim.set_m((1, 0, 0)) H0 = 1e5 sim.add(Zeeman((0, 0, H0))) ts = np.linspace(0, 1e-9, 101) mx = [] my = [] mz = [] real_ts = [] for t in ts: sim.run_until(t) real_ts.append(sim.t) print sim.t, abs(sim.spin_length()[0] - 1) mx.append(sim.spin[0]) my.append(sim.spin[1]) mz.append(sim.spin[2]) mz = np.array(mz) # print mz a_mx, a_my, a_mz = single_spin(alpha, gamma, H0, ts) print sim.stat() if do_plot: ts_ns = np.array(real_ts) * 1e9 plt.plot(ts_ns, mx, ".", label="mx", color='DarkGreen') plt.plot(ts_ns, my, ".", label="my", color='darkslateblue') plt.plot(ts_ns, mz, ".", label="mz", color='m') plt.plot(ts_ns, a_mx, "--", label="analytical", color='b') plt.plot(ts_ns, a_my, "--", color='b') plt.plot(ts_ns, a_mz, "--", color='b') plt.xlabel("time (ns)") plt.ylabel("m") plt.title("integrating a macrospin") plt.legend() plt.savefig("single_spin.pdf") print("Max Deviation = {0}".format( np.max(np.abs(mz - a_mz)))) assert np.max(np.abs(mz - a_mz)) < 5e-7
def relax_neb(k, maxst, simname, init_im, interp, save_every=10000): """ Execute a simulation with the NEB function of the FIDIMAG code, for a nano disk The simulations are made for a specific spring constant 'k' (a float), number of images 'init_im', interpolations between images 'interp' (an array) and a maximum of 'maxst' steps. 'simname' is the name of the simulation, to distinguish the output files. --> vtks and npys are saved in folders starting with the 'simname' """ # Prepare simulation # We define the small cylinder with the Magnetisation function sim = Sim(mesh) sim.Ms = cylinder # Energies # Exchange sim.add(UniformExchange(A=A)) # Bulk DMI --> This produces a Bloch DW - like skyrmion sim.add(DMI(D=D)) # No Demag, but this could have some effect # Demagnetization energy # sim.add(Demag()) # Initial images (npy files or functions) init_images = init_im # Number of images between each state specified before (here we need only # two, one for the states between the initial and intermediate state # and another one for the images between the intermediate and final # states). Thus, the number of interpolations must always be # equal to 'the number of initial states specified', minus one. interpolations = interp # Initiate the NEB algorithm driver neb = NEB_Sundials(sim, init_images, interpolations=interpolations, spring=k, name=simname) # Start the relaxation neb.relax(max_steps=maxst, save_vtk_steps=save_every, save_npy_steps=save_every, stopping_dmdt=1)
def setup_domain_wall_cobalt(node_count=NODE_COUNT, A=A_Co, Ms=Ms_Co, K1=K1_Co, length=LENGTH, do_precession=True, unit_length=UNIT_LENGTH): a = length / node_count # cell size mesh = CuboidMesh(dx=a, dy=a, dz=a, nx=node_count, ny=1, nz=1, unit_length=unit_length) sim = Sim(mesh, "dw_cobalt") sim.Ms = Ms sim.set_m(lambda r: initial_m(r, length)) sim.do_precession = do_precession sim.add(UniformExchange(A)) sim.add(UniaxialAnisotropy(K1, (0, 0, 1))) sim.pins = lambda r: 1 if (r[0] < a or r[0] > LENGTH - a) else 0 return sim
def create_simulation(mesh): sim = Sim(mesh) sim.Ms = 8.6e5 sim.set_m((1, 0, 0)) sim.add(UniformExchange(A=1.3e-11)) # sim.add(Demag()) #sim.add(UniaxialAnisotropy(Kx, (1, 0, 0), name='Kx')) anis = UniaxialAnisotropy(1e5, axis=(1, 0, 0)) sim.add(anis) return sim
def run(integrator, jacobian): name = "sim_" + integrator if integrator == "sundials": name += "_J1" if jacobian else "_J0" sim = Sim(mesh, name, integrator, use_jac=jacobian) sim.Ms = 0.86e6 sim.alpha = 0.5 sim.set_m((1, 0, 1)) sim.add(UniformExchange(A=13e-12)) sim.add(Demag()) ts = np.linspace(0, 3e-10, 61) for t in ts: sim.run_until(t)
def relax_system(mesh): sim = Sim(mesh, name='relax') sim.set_tols(rtol=1e-6, atol=1e-6) sim.alpha = 0.5 sim.gamma = 2.211e5 sim.Ms = 8.6e5 sim.do_precession = False sim.set_m(init_m) #sim.set_m((0,0.1,1)) #sim.set_m(np.load('m0.npy')) A = 1.3e-11 exch = UniformExchange(A=A) sim.add(exch) dmi = DMI(D=1.3e-3) sim.add(dmi) anis = UniaxialAnisotropy(-3.25e4, axis=(0, 0, 1)) sim.add(anis) zeeman = Zeeman((0, 0, 6.014576e4)) sim.add(zeeman, save_field=True) sim.relax(dt=1e-13, stopping_dmdt=0.5, max_steps=5000, save_m_steps=None, save_vtk_steps=50) np.save('m0.npy', sim.spin)
def test_zeeman(): mesh = CuboidMesh(nx=5, ny=2, nz=1) sim = Sim(mesh) sim.set_m((1, 0, 0)) zeeman = Zeeman(varying_field) sim.add(zeeman) field = zeeman.compute_field() assert field[6] == 1.2 * (2 + 0.5) assert field[7] == 2.3 * 0.5
def relax_system(): mesh = CuboidMesh(nx=1, ny=1, nz=1) sim = Sim(mesh, name='relax') sim.driver.set_tols(rtol=1e-10, atol=1e-10) sim.driver.alpha = 0.5 sim.set_m((1.0, 0, 0)) sim.add(Zeeman((0, 0, 1e5))) ts = np.linspace(0, 1e-9, 1001) for t in ts: sim.run_until(t)
def run_sim(): mesh = CuboidMesh() sim = Sim(mesh, name='spin') alpha = 0.1 gamma = 2.21e5 sim.alpha = alpha sim.driver.gamma = gamma sim.mu_s = 1.0 sim.set_m((1, 0, 0)) H0 = 1e5 sim.add(Zeeman((0, 0, H0))) sim.driver.run_until(1e-10) sim.driver.run_until(0.5e-10)
def test_sim_pin(): mesh = CuboidMesh(nx=3, ny=2, nz=1) sim = Sim(mesh) sim.set_m((0, 0.8, 0.6)) sim.alpha = 0.1 sim.gamma = 1.0 sim.pins = pin_fun anis = UniaxialAnisotropy(Ku=1, axis=[0, 0, 1], name='Dx') sim.add(anis) sim.run_until(1.0) print sim.spin assert sim.spin[0] == 0 assert sim.spin[2] != 0
def test_sim_pin(): mesh = CuboidMesh(nx=3, ny=2, nz=1) sim = Sim(mesh, integrator='sundials_openmp') sim.set_m((0, 0.8, 0.6)) sim.alpha = 0.1 sim.driver.gamma = 1.0 sim.pins = pin_fun anis = UniaxialAnisotropy(Ku=1, axis=[0, 0, 1], name='Dx') sim.add(anis) sim.driver.run_until(1.0) print(sim.spin) assert sim.spin[0] == 0 assert sim.spin[2] != 0
def test_exch_1d(do_plot=False): # Initiate the 1D mesh and magnetisation as before mesh = CuboidMesh(nx=100, ny=1, nz=1) sim = Sim(mesh) sim.set_m(init_m) # Simplify the magnetic parameters mu0 = 4 * np.pi * 1e-7 sim.Ms = 1.0 / mu0 exch = UniformExchange(1) sim.add(exch) # Compute the exchange field and reshape it in order # to leave every row as the [f_x, f_y, f_z] array # for every spin field = exch.compute_field() field.shape = (-1, 3) # We know that the field in x is always zero ( see the # analytical calculation at the beginning) assert max(abs(field[:, 0])) == 0 # These are the analytical values for the exchange field in y,z # In this case, k=0.1 , then 2 * k^2 evaluates as 0.02 xs = np.linspace(0, 99, 100) epy = -0.02 * np.sin(0.1 * xs) epz = -0.02 * np.cos(0.1 * xs) # Compare the analytical value # of the y component of the exchange field, with Fidimag's # result (second column of the reshaped field array) # WARNING: NOTICE that we are not considering the extremes since # there is a wrong expression in the border of the exchange field # with NO PBCs. We must FIX this test! assert max(abs(epy[1:-1] - field[1:-1, 1])) < 3e-5 if do_plot: plt.plot(xs, field[:, 1], "-.", label="my", color='DarkGreen') plt.plot(xs, field[:, 2], "-.", label="mz", color='DarkGreen') plt.plot(xs, epy, "--", label="analytical", color='b') plt.plot(xs, epz, "--", color='r') plt.xlabel("xs") plt.ylabel("field") plt.legend() plt.savefig("exchange_field.pdf")
def test_demag_field_oommf_large(Ms=8e5, A=1.3e-11): mesh = CuboidMesh(nx=150, ny=50, nz=1, dx=2.5, dy=2.5, dz=3, unit_length=1e-9) sim = Sim(mesh) sim.Ms = Ms exch = UniformExchange(A=A) sim.add(exch) demag = Demag() sim.add(demag) def init_m(pos): x, y, z = pos return (np.sin(x) + y + 2.3 * z, np.cos(x) + y + 1.3 * z, 0) sim.set_m(init_m) demag_field = demag.compute_field() exch_field = exch.compute_field() #exact = demag.compute_exact() init_m0 = """ return [list [expr {sin($x*1e9)+$y*1e9+$z*2.3e9}] [expr {cos($x*1e9)+$y*1e9+$z*1.3e9}] 0] """ #demag_oommf = compute_demag_field(mesh, Ms=Ms, init_m0=init_m0) #exch_oommf = compute_exch_field(mesh, Ms=Ms, init_m0=init_m0, A=A) omf_file = os.path.join(os.path.dirname(os.path.abspath(__file__)),'omfs','test_demag_field_oommf_large_Demag.ohf') ovf = OMF2(omf_file) demag_oommf = ovf.get_all_mags() omf_file = os.path.join(os.path.dirname(os.path.abspath(__file__)),'omfs','test_demag_field_oommf_large_Exchange.ohf') ovf = OMF2(omf_file) exch_oommf = ovf.get_all_mags() mx0, mx1, mx2 = compare_fields(demag_oommf, demag_field) #print mx0, mx1, mx2 assert max([mx0,mx1,mx2])< 5e-10 mx0, mx1, mx2 = compare_fields(exch_oommf, exch_field) #print mx0, mx1, mx2 assert max([mx0, mx1, mx2]) < 1e-11
def relax_neb(k, maxst, simname, init_im, interp, save_every=10000): """ Execute a simulation with the NEB function of the FIDIMAG code, for an elongated particle (long cylinder) The simulations are made for a specific spring constant 'k' (a float), number of images 'init_im', interpolations between images 'interp' (an array) and a maximum of 'maxst' steps. 'simname' is the name of the simulation, to distinguish the output files. --> vtks and npys are saved in files starting with the 'simname' string """ # Prepare simulation # We define the cylinder with the Magnetisation function sim = Sim(mesh) sim.Ms = two_part #sim.add(UniformExchange(A=A)) # Uniaxial anisotropy along x-axis sim.add(UniaxialAnisotropy(Kx, axis=(1, 0, 0))) # Define many initial states close to one extreme. We want to check # if the images in the last step, are placed mostly in equally positions init_images = init_im # Number of images between each state specified before (here we need only # two, one for the states between the initial and intermediate state # and another one for the images between the intermediate and final # states). Thus, the number of interpolations must always be # equal to 'the number of initial states specified', minus one. interpolations = interp neb = NEB_Sundials(sim, init_images, interpolations=interpolations, spring=k, name=simname) neb.relax(max_steps=maxst, save_vtk_steps=save_every, save_npy_steps=save_every, stopping_dmdt=1e-2)
def test_demag_field_oommf(Ms=6e5): mesh = CuboidMesh(nx=5, ny=2, nz=3, unit_length=1e-9) sim = Sim(mesh) sim.Ms = Ms demag = Demag() sim.add(demag) def init_m(pos): x = pos[0] if x <= 2: return (1, 0, 0) elif x >= 4: return (0, 0, 1) else: return (0, 1, 0) sim.set_m(init_m) field = demag.compute_field() exact = demag.compute_exact() init_m0 = """ if { $x <=2e-9 } { return "1 0 0" } elseif { $x >= 4e-9 } { return "0 0 1" } else { return "0 1 0" } """ field_oommf = compute_demag_field(mesh, Ms=Ms, init_m0=init_m0) mx0, mx1, mx2 = compare_fields(field_oommf, exact) print mx0, mx1, mx2 assert max([mx0, mx1, mx2]) < 2e-14 mx0, mx1, mx2 = compare_fields(field_oommf, field) print mx0, mx1, mx2 assert np.max(abs(field - field_oommf)) < 2e-9
def excite_system(mesh, beta=0.0): # Specify the stt dynamics in the simulation sim = Sim(mesh, name='dyn_%g'%beta, driver='llg_stt_cpp') sim.driver.set_tols(rtol=1e-12, atol=1e-12) sim.driver.alpha = 0.1 sim.driver.gamma = 2.211e5 sim.Ms = 8.6e5 # sim.set_m(init_m) sim.set_m(np.load('m0.npy')) # Energies A = 1.3e-11 exch = UniformExchange(A=A) sim.add(exch) anis = UniaxialAnisotropy(5e4) sim.add(anis) # beta is the parameter in the STT torque sim.a_J = global_const*1e11 sim.p = (1,0,0) sim.beta = beta # The simulation will run for 5 ns and save # 500 snapshots of the system in the process ts = np.linspace(0, 0.5e-9, 21) xs=[] thetas=[] for t in ts: print('time', t) sim.run_until(t) spin = sim.spin.copy() x, theta = extract_dw(spin) xs.append(x) thetas.append(theta) sim.save_vtk() np.savetxt('dw_%g.txt'%beta,np.transpose(np.array([ts, xs,thetas])))
def relax_system_only_exchange(mesh): sim = Sim(mesh, name='relax_exchange_only') sim.set_tols(rtol=1e-6, atol=1e-6) sim.alpha = 0.5 sim.gamma = 2.211e5 sim.Ms = 8.6e5 sim.do_precession = False sim.set_m(init_m_BP) A = 1.3e-11 exch = UniformExchange(A=A) sim.add(exch) sim.relax(dt=1e-13, stopping_dmdt=0.5, max_steps=5000, save_m_steps=None, save_vtk_steps=50) np.save('m0.npy', sim.spin)
def relax_system(mesh): sim = Sim(mesh, name='relax') sim.set_tols(rtol=1e-6, atol=1e-6) sim.alpha = 0.5 sim.gamma = 2.211e5 sim.Ms = 8.6e5 sim.do_procession = False sim.set_m(init_m) exch = UniformExchange(A=1.3e-11) sim.add(exch) dmi = DMI(D=-4e-3) sim.add(dmi) zeeman = Zeeman((0, 0, 4e5)) sim.add(zeeman, save_field=True) sim.relax(dt=1e-13, stopping_dmdt=1e-2, save_m_steps=None, save_vtk_steps=50) np.save('m0.npy', sim.spin)
def test_dw_dmi(mesh=mesh, do_plot=False): Ms = 8.0e5 sim = Sim(mesh, name='relax') sim.set_m(m_init_dw) sim.driver.set_tols(rtol=1e-8, atol=1e-12) sim.Ms = Ms sim.alpha = 0.5 sim.do_precession = False A = 1.3e-11 D = 4e-4 Kx = 8e4 Kp = -6e5 sim.add(UniformExchange(A)) sim.add(DMI(D)) sim.add(UniaxialAnisotropy(Kx, axis=[1, 0, 0], name='Kx')) sim.driver.relax(stopping_dmdt=0.01) xs = np.array([p[0] for p in mesh.coordinates]) mx, my, mz = analytical(xs, A=A, D=D, K=Kx) mxyz = sim.spin.copy() mxyz = mxyz.reshape(-1, 3) assert max(abs(mxyz[:, 0] - mx)) < 0.002 assert max(abs(mxyz[:, 1] - my)) < 0.002 assert max(abs(mxyz[:, 2] - mz)) < 0.0006 if do_plot: save_plot(mxyz, mx, my, mz)
def relax_system(mesh): sim = Sim(mesh, name='relax') sim.set_tols(rtol=1e-10, atol=1e-14) sim.alpha = 0.5 sim.gamma = 2.211e5 sim.Ms = 8.6e5 sim.do_precession = False sim.set_m(init_m) # sim.set_m(np.load('m0.npy')) A = 1.3e-11 exch = UniformExchange(A=A) sim.add(exch) dmi = DMI(D=1e-3) sim.add(dmi) zeeman = Zeeman((0, 0, 2e4)) sim.add(zeeman, save_field=True) sim.relax(dt=1e-13, stopping_dmdt=0.01, max_steps=5000, save_m_steps=None, save_vtk_steps=50) np.save('m0.npy', sim.spin)
def relax_system(mesh): sim = Sim(mesh, chi=1e-3, name='relax', driver='llbar_full') sim.driver.set_tols(rtol=1e-7, atol=1e-7) sim.Ms = 8.0e5 sim.driver.alpha = 0.1 sim.beta = 0 sim.driver.gamma = 2.211e5 sim.set_m((1, 0.25, 0.1)) # sim.set_m(np.load('m0.npy')) A = 1.3e-11 exch = UniformExchange(A=A) sim.add(exch) mT = 795.7747154594767 zeeman = Zeeman([-100 * mT, 4.3 * mT, 0], name='H') sim.add(zeeman, save_field=True) demag = Demag() sim.add(demag) ONE_DEGREE_PER_NS = 17453292.52 sim.relax(dt=1e-12, stopping_dmdt=0.01, max_steps=5000, save_m_steps=100, save_vtk_steps=50) np.save('m0.npy', sim.spin)
def apply_field1(mesh): sim = Sim(mesh, name='dyn') sim.set_tols(rtol=1e-10, atol=1e-10) sim.alpha = 0.02 sim.gamma = 2.211e5 sim.Ms = 8.0e5 sim.set_m(np.load('m0.npy')) A = 1.3e-11 exch = UniformExchange(A=A) sim.add(exch) demag = Demag() sim.add(demag) mT = 0.001 / mu0 print("Applied field = {}".format(mT)) zeeman = Zeeman([-24.6 * mT, 4.3 * mT, 0], name='H') sim.add(zeeman, save_field=True) ts = np.linspace(0, 1e-9, 201) for t in ts: sim.run_until(t) print('sim t=%g' % t)
def relax_system(mesh): sim = Sim(mesh, name='relax') sim.driver.set_tols(rtol=1e-6, atol=1e-6) sim.driver.alpha = 0.5 sim.driver.gamma = 2.211e5 sim.Ms = 8.6e5 sim.do_precession = False sim.set_m(init_m) exch = UniformExchange(A=1.3e-11) sim.add(exch) dmi = DMI(D=-4e-3) sim.add(dmi) zeeman = Zeeman((0, 0, 4e5)) sim.add(zeeman, save_field=True) sim.relax(dt=1e-13, stopping_dmdt=1e-2, save_m_steps=None, save_vtk_steps=50) np.save('m0.npy', sim.spin)
def excite_system(mesh, time=5, snaps=501): # Specify the stt dynamics in the simulation sim = Sim(mesh, name='dyn', driver='llg_stt') # Set the simulation parameters sim.set_tols(rtol=1e-12, atol=1e-14) sim.alpha = 0.05 sim.gamma = 2.211e5 sim.Ms = 8.6e5 # Load the initial state from the npy file saved # in the realxation sim.set_m(np.load('m0.npy')) # Add the energies A = 1.3e-11 exch = UniformExchange(A=A) sim.add(exch) anis = UniaxialAnisotropy(5e4) sim.add(anis) # dmi = DMI(D=8e-4) # sim.add(dmi) # Set the current in the x direction, in A / m # beta is the parameter in the STT torque sim.jx = -1e12 sim.beta = 1 # The simulation will run for x ns and save # 'snaps' snapshots of the system in the process ts = np.linspace(0, time * 1e-9, snaps) for t in ts: print 'time', t sim.run_until(t) sim.save_vtk() sim.save_m()
def relax_system(mesh): sim = Sim(mesh, name="relax") sim.driver.set_tols(rtol=1e-10, atol=1e-14) sim.driver.alpha = 0.5 sim.driver.gamma = 2.211e5 sim.Ms = 8.6e5 sim.do_precession = False sim.set_m(init_m) # sim.set_m(np.load('m0.npy')) A = 1.3e-11 exch = UniformExchange(A=A) sim.add(exch) dmi = DMI(D=1e-3) sim.add(dmi) zeeman = Zeeman((0, 0, 2e4)) sim.add(zeeman, save_field=True) sim.relax(dt=1e-13, stopping_dmdt=0.01, max_steps=5000, save_m_steps=None, save_vtk_steps=50) np.save("m0.npy", sim.spin)
def create_simulation(mesh, simname): # Initiate a simulation object. PBCs are specified in the mesh sim = Sim(mesh, name=simname) # Use default gamma value # sim.gamma = const.gamma # Magnetisation in A/m sim.Ms = 148367 # We could change the parameters using this option # sim.set_options(gamma=const.gamma) # Initial magnetisation profile from the function sim.set_m((0, 0.2, 0.8)) # Exchange constant A = 1.602e-12 exch = UniformExchange(A) sim.add(exch) # DMI constant D = 3.84e-3 dmi = DMI(D, dmi_type='interfacial') sim.add(dmi) # Zeeman field sim.add(Zeeman((0, 0, 25. / c.mu_0))) # Tune the damping for faster convergence sim.driver.alpha = 0.5 # Remove precession sim.driver.do_precession = False sim.driver.set_tols(rtol=1e-12, atol=1e-12) return sim
def apply_field1(mesh): sim = Sim(mesh, name='dyn') sim.driver.set_tols(rtol=1e-10, atol=1e-10) sim.driver.alpha = 0.02 sim.driver.gamma = 2.211e5 sim.Ms = 8.0e5 sim.set_m(np.load('m0.npy')) A = 1.3e-11 exch = UniformExchange(A=A) sim.add(exch) demag = Demag() sim.add(demag) mT = 0.001 / mu0 print("Applied field = {}".format(mT)) zeeman = Zeeman([-24.6 * mT, 4.3 * mT, 0], name='H') sim.add(zeeman, save_field=True) ts = np.linspace(0, 1e-9, 201) for t in ts: sim.run_until(t) print('sim t=%g' % t)
def run_fidimag(mesh): mu0 = 4 * np.pi * 1e-7 Ms = 8.6e5 A = 16e-12 D = -3.6e-3 K = 510e3 sim = Sim(mesh) sim.set_tols(rtol=1e-10, atol=1e-10) sim.alpha = 0.5 sim.gamma = 2.211e5 sim.Ms = Ms sim.do_precession = False sim.set_m((0, 0, 1)) sim.add(UniformExchange(A)) sim.add(DMI(D, type='interfacial')) sim.add(UniaxialAnisotropy(K, axis=(0, 0, 1))) sim.relax(dt=1e-13, stopping_dmdt=0.01, max_steps=5000, save_m_steps=None, save_vtk_steps=50) m = sim.spin return m.copy()
def elongated_part_sim(): sim = Sim(mesh) sim.Ms = lambda r: cylinder(r, centre, 8) sim.add(UniformExchange(A=A)) sim.add(UniaxialAnisotropy(Kx, axis=(0, 1, 0))) # Anisotropy along y sim.add(Demag()) return sim
def test_energy_dmi(Ms=8e5, D=1.32e-3): mesh = CuboidMesh(nx=40, ny=50, nz=1, dx=2.5, dy=2.5, dz=3, unit_length=1e-9) sim = Sim(mesh) sim.Ms = Ms dmi = DMI(D=D, type='interfacial') #dmi = DMI(D=D, type='bulk') sim.add(dmi) def init_m(pos): x, y, z = pos return (np.sin(x) + y + 2.3 * z, np.cos(x) + y + 1.3 * z, 1) sim.set_m(init_m) dmi_energy = dmi.compute_energy() # init_m0=""" # return [list [expr {sin($x*1e9)+$y*1e9+$z*2.3e9}] [expr {cos($x*1e9)+$y*1e9+$z*1.3e9}] 1] #""" #field_oommf = compute_dmi_field(mesh, Ms=Ms, init_m0=init_m0, D=D) dmi_energy_oommf = -4.5665527749090378e-20 print('dmi energy', dmi_energy) assert abs(dmi_energy - dmi_energy_oommf) / dmi_energy_oommf < 1e-15
def excite_system(mesh): # Specify the stt dynamics in the simulation sim = Sim(mesh, name='dyn2', driver='llg_stt') sim.driver.set_tols(rtol=1e-12, atol=1e-14) sim.driver.alpha = 0.2 sim.driver.gamma = 2.211e5 sim.Ms = 8.6e5 # sim.set_m(init_m) sim.set_m(np.load('m0.npy')) # Energies A = 1.3e-11 exch = UniformExchange(A=A) sim.add(exch) anis = UniaxialAnisotropy(5e4) sim.add(anis) # dmi = DMI(D=8e-4) # sim.add(dmi) # Set the current in the x direction, in A / m # beta is the parameter in the STT torque sim.driver.jx = -1e12 sim.driver.beta = 0.01 # The simulation will run for 5 ns and save # 500 snapshots of the system in the process ts = np.linspace(0, 5e-9, 501) for t in ts: print('time', t) sim.driver.run_until(t) sim.save_vtk() sim.save_m()
def relax_system(mesh): # Only relaxation sim = Sim(mesh, name='relax') # Simulation parameters sim.driver.set_tols(rtol=1e-8, atol=1e-10) sim.driver.alpha = 0.5 sim.driver.gamma = 2.211e5 sim.Ms = 8.6e5 sim.driver.do_precession = False # The initial state passed as a function sim.set_m(init_m) # sim.set_m(np.load('m0.npy')) # Energies A = 1.3e-11 exch = UniformExchange(A=A) sim.add(exch) anis = UniaxialAnisotropy(5e4) sim.add(anis) # dmi = DMI(D=8e-4) # sim.add(dmi) # mT = 795.7747154594767 # ONE_DEGREE_PER_NS = 17453292.52 # Start relaxation and save the state in m0.npy sim.relax(dt=1e-14, stopping_dmdt=0.01, max_steps=5000, save_m_steps=None, save_vtk_steps=50) np.save('m0.npy', sim.spin)
def test_compute_field(): """In an infinite film, we expect the demag tensor to be (0, 0, -1), and thus the magnetisation, if aligned in 0, 0, 1 direction, to create a demag field pointing with equal strength in the opposite direction. """ mesh = CuboidMesh(nx=1, ny=1, nz=1, dx=2.0, dy=2.0, dz=2.0, unit_length=1e-9, periodicity=(True, True, False)) sim = Sim(mesh, name='relax') sim.driver.set_tols(rtol=1e-10, atol=1e-14) sim.alpha = 0.5 sim.gamma = 2.211e5 sim.Ms = 8.6e5 sim.do_precession = False sim.set_m((0, 0, 1)) demag = Demag(pbc_2d=True) sim.add(demag) field = demag.compute_field() print((1 + field[2] / 8.6e5)) assert abs(1 + field[2] / 8.6e5) < 1e-10
def excite_system(mesh): sim = Sim(mesh, name='dyn') sim.driver.set_tols(rtol=1e-10, atol=1e-14) sim.driver.alpha = 0.01 sim.driver.gamma = 2.211e5 sim.Ms = spatial_Ms # sim.set_m(init_m) sim.set_m(np.load('m0.npy')) A = 1.3e-11 exch = UniformExchange(A=A) sim.add(exch) demag = Demag(pbc_2d=True) sim.add(demag) mT = 795.7747154594767 sigma = 0.08e-9 def gaussian_fun(t): return np.exp(-0.5 * (t / sigma)**2) zeeman = TimeZeeman((80 * mT, 0, 0), time_fun=gaussian_fun, name='hx') #zeeman = Zeeman((100*mT,0,0), name='hx') sim.add(zeeman, save_field=True) ts = np.linspace(0, 1e-9, 501) for t in ts: print('time', t) print('length:', sim.spin_length()[0:200]) sim.run_until(t) sim.save_vtk()
def excite_system(mesh): sim = Sim(mesh, name='dyn', driver='llg_stt') sim.set_tols(rtol=1e-8, atol=1e-10) sim.alpha = 0.5 sim.gamma = 2.211e5 sim.Ms = 8.6e5 sim.set_m(np.load('m0.npy')) exch = UniformExchange(A=1.3e-11) sim.add(exch) dmi = DMI(D=-4e-3) sim.add(dmi) zeeman = Zeeman((0, 0, 4e5)) sim.add(zeeman, save_field=True) sim.jx = -5e12 sim.beta = 0 ts = np.linspace(0, 0.5e-9, 101) for t in ts: print 'time', t sim.run_until(t) sim.save_vtk()
def relax_neb(mesh, k, maxst, simname, init_im, interp, save_every=10000, stopping_dYdt=0.01): """ Execute a simulation with the NEBM algorithm of the FIDIMAG code Here we use always the 21x21 Spins Mesh and don't vary the material parameters. This can be changed adding those parameters as variables. We create a new Simulation object every time this function is called since it can be modified in the process k :: NEBM spring constant maxst :: Maximum number of iterations simname :: Simulation name. VTK and NPY files are saved in folders starting with the 'simname' string init_im :: A list with magnetisation states (usually loaded from NPY files or from a function) that will be used as images in the energy band, e.g. for two states: [np.load('skyrmion.npy'), np.load('ferromagnet.npy')] interp :: Array or list with the numbers of interpolations between every pair of the 'init_im' list. The length of this array is: len(__init_im) - 1 save_every :: Save VTK and NPY files every 'save_every' number of steps """ # Initialise a simulation object and set the default gamma for the LLG # equation sim = Sim(mesh, name=simname) # sim.gamma = const.gamma # Magnetisation in A/m sim.Ms = 148367 # Interactions ------------------------------------------------------------ # Exchange constant A = 1.602e-12 exch = UniformExchange(A) sim.add(exch) # DMI constant D = 3.84e-3 dmi = DMI(D, dmi_type='interfacial') sim.add(dmi) # Zeeman field sim.add(Zeeman((0, 0, 25. / c.mu_0))) # ------------------------------------------------------------------------- # Set the initial images from the list init_images = init_im # The number of interpolations must always be # equal to 'the number of initial states specified', minus one. interpolations = interp # Start a NEB simulation passing the Simulation object and all the NEB # parameters neb = NEBM_Geodesic(sim, init_images, interpolations=interpolations, spring_constant=k, name=simname, ) # Finally start the energy band relaxation neb.relax(max_iterations=maxst, save_vtks_every=save_every, save_npys_every=save_every, stopping_dYdt=stopping_dYdt ) # Produce a file with the data from a cubic interpolation for the band interp_data = np.zeros((200, 2)) interp_data[:, 0], interp_data[:, 1] = neb.compute_polynomial_approximation(200) np.savetxt(simname + 'interpolation.dat', interp_data)
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 sim.relax()
def relax_neb(k, maxst, simname, init_im, interp, save_every=10000, coordinates='Cartesian'): """ Execute a simulation with the NEB function of the FIDIMAG code, for an elongated particle (long cylinder) The simulations are made for a specific spring constant 'k' (a float), number of images 'init_im', interpolations between images 'interp' (an array) and a maximum of 'maxst' steps. 'simname' is the name of the simulation, to distinguish the output files. --> vtks and npys are saved in files starting with the 'simname' string """ # Prepare simulation # We define the cylinder with the Magnetisation function sim = Sim(mesh) sim.Ms = two_part #sim.add(UniformExchange(A=A)) # Uniaxial anisotropy along x-axis sim.add(UniaxialAnisotropy(Kx, axis=(1, 0, 0))) # Define many initial states close to one extreme. We want to check # if the images in the last step, are placed mostly in equally positions init_images = init_im # Number of images between each state specified before (here we need only # two, one for the states between the initial and intermediate state # and another one for the images between the intermediate and final # states). Thus, the number of interpolations must always be # equal to 'the number of initial states specified', minus one. interpolations = interp if coordinates == 'Cartesian': neb = NEBM_Cartesian(sim, init_images, interpolations=interpolations, spring_constant=k, name=simname ) if coordinates == 'Spherical': neb = NEBM_Spherical(sim, init_images, interpolations=interpolations, spring_constant=k, name=simname ) if coordinates == 'Geodesic': neb = NEBM_Geodesic(sim, init_images, interpolations=interpolations, spring_constant=k, name=simname ) neb.relax(max_iterations=maxst, save_vtks_every=save_every, save_npys_every=save_every, stopping_dYdt=1e-2)
centre_x = (mesh.coordinates[:, 0].max() + mesh.coordinates[:, 0].min()) * 0.5 + mesh.coordinates[:, 0].min() centre_y = (mesh.coordinates[:, 1].max() + mesh.coordinates[:, 1].min()) * 0.5 + mesh.coordinates[:, 1].min() centre_z = 0.5 # ----------------------------------------------------------------------------- sim = Sim(mesh, name='dynamics') sim.set_m(np.load('initial_state.npy')) # ----------------------------------------------------------------------------- sim.Ms = Ms sim.add(UniformExchange(A)) sim.add(Demag()) # sim.add(UniaxialAnisotropy(Ku, (0, 0, 1))) # Periodic DMI sim.add(DMI(D, dmi_type='interfacial')) # External field along the stripe length sim.add(Zeeman((0, B0 / mu0, 0)), save_field=True) # ----------------------------------------------------------------------------- # Dynamics def spatial_sinc_field(r, x0, y0, z0, h0):
# We define the cylinder with the Magnetisation function sim = Sim(mesh, name='skyrmion') sim.Ms = cylinder # To get a faster relaxation, we tune the LLG equation parameters sim.do_precession = False sim.alpha = 0.5 # Initial magnetisation: sim.set_m(init_m) # Energies: # Exchange sim.add(UniformExchange(A=A)) # Bulk DMI sim.add(DMI(D=D)) # Relax the system sim.relax(dt=1e-12, stopping_dmdt=0.0001, max_steps=5000, save_m_steps=None, save_vtk_steps=None) # Save the final relaxed state and a vtk file np.save('sk_up.npy', sim.spin) sim.save_vtk()
# ----------------------------------------------------------------------------- sim = Sim(mesh) sim.driver.gamma = 2.21e5 sim.set_m((0.1, 0.9, 0)) # ----------------------------------------------------------------------------- A = 13e-12 # J * m**-1 D = 3e-3 # J * m**-2 Ku = 0e6 # J * m**-3 Ms = 0.86e6 # A / m B0 = 0.4 # T sim.Ms = Ms sim.add(UniformExchange(A)) sim.add(Demag()) # sim.add(UniaxialAnisotropy(Ku, (0, 0, 1))) # Periodic DMI sim.add(DMI(D, dmi_type='interfacial')) # External field along the stripe length sim.add(Zeeman((0, B0 / mu0, 0)), save_field=True) # ----------------------------------------------------------------------------- # Relax the system first sim.driver.alpha = 0.9 sim.driver.do_precession = False sim.driver.relax(stopping_dmdt=0.01)
# Initiate Fidimag simulation --------------------------------------------- sim = Sim(mesh, name=args.sim_name) # sim.driver.set_tols(rtol=1e-10, atol=1e-14) sim.driver.alpha = args.alpha # sim.driver.gamma = 2.211e5 if args.no_precession: sim.do_precession = False # Material parameters ----------------------------------------------------- sim.Ms = args.Ms exch = UniformExchange(A=args.A) sim.add(exch) dmi = DMI(D=(args.D * 1e-3), type='interfacial') sim.add(dmi) if args.B: zeeman = Zeeman((0, 0, args.B / mu0)) sim.add(zeeman, save_field=True) if args.k_u: # Uniaxial anisotropy along + z-axis sim.add(UniaxialAnisotropy(args.k_u, axis=(0, 0, 1))) if args.Demag: print 'Using Demag!' sim.add(Demag())
def test_with_oommf_spatial_Ms(A=1e-11): def spatial_Ms(pos): x, y = pos[0], pos[1] if x**2 + y**2 < 5**2: return 2e4 else: return 0 init_m0 = """ return [list [expr {sin($x*1e9)+$y*1e9+$z*2.3e9}] [expr {cos($x*1e9)+$y*1e9+$z*1.3e9}] 0] """ init_Ms = """ if { $x*$x + $y*$y < 5e-9*5e-9 } { return 2e4 } else { return 0 } """ mesh = CuboidMesh(nx=12, ny=10, nz=2, dx=0.5, unit_length=1e-9) sim = Sim(mesh) sim.Ms = spatial_Ms exch = UniformExchange(A=A) sim.add(exch) demag = Demag() sim.add(demag) def init_m(pos): x, y, z = pos return (np.sin(x) + y + 2.3 * z, np.cos(x) + y + 1.3 * z, 0) sim.set_m(init_m) field = exch.compute_field() #field_oommf = compute_exch_field(mesh, init_m0=init_m0, A=A, spatial_Ms=init_Ms) omf_file = os.path.join(os.path.dirname(os.path.abspath(__file__)),'omfs','test_with_oommf_spatial_Ms_Exchange.ohf') ovf = OMF2(omf_file) field_oommf = ovf.get_all_mags() mx0, mx1, mx2 = compare_fields(field_oommf, field) assert max([mx0, mx1, mx2]) < 1e-12 field = demag.compute_field() #field_oommf = compute_demag_field(mesh, spatial_Ms=init_Ms, init_m0=init_m0) omf_file = os.path.join(os.path.dirname(os.path.abspath(__file__)),'omfs','test_with_oommf_spatial_Ms_Demag.ohf') ovf = OMF2(omf_file) field_oommf = ovf.get_all_mags() mx0, mx1, mx2 = compare_fields(field_oommf, field) assert max([mx0, mx1, mx2]) < 1e-11