def test_sim_single_spin_sllg(do_plot=False): mesh = CuboidMesh(nx=1, ny=1, nz=1) sim = Sim(mesh, name='spin', driver='sllg') alpha = 0.1 gamma = 2.21e5 sim.set_options(dt=5e-15, gamma=gamma) sim.alpha = alpha sim.mu_s = 1.0 sim.set_m((1, 0, 0)) H0 = 1e5 sim.add(Zeeman((0, 0, H0))) ts = np.linspace(0, 1e-10, 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) a_mx, a_my, a_mz = single_spin(alpha, gamma, H0, ts) if do_plot: plot(real_ts, mx, my, mz, a_mx, a_my, a_mz, name='spin_sllg.pdf', title='integrating a spin') print(("Max Deviation = {0}".format(np.max(np.abs(mz - a_mz))))) assert np.max(np.abs(mz - a_mz)) < 1e-8
def disable_test_sim_single_spin_llg_stt(do_plot=False): ni = Nickel() mesh = CuboidMesh(nx=1, ny=1, nz=1) mesh.set_material(ni) ni.alpha = 0.1 sim = Sim(mesh, driver='llg_stt') sim.set_m((1, 0, 0)) H0 = 1 sim.add(Zeeman((0, 0, H0))) dt = 1e-12 ts = np.linspace(0, 200 * dt, 101) precession = ni.gamma / (1 + ni.alpha**2) mz_ref = [] mxyz = [] real_ts = [] for t in ts: sim.run_until(t) real_ts.append(sim.t) print(sim.t, abs(sim.spin_length()[0] - 1), sim.spin) mz_ref.append(np.tanh(precession * ni.alpha * H0 * sim.t)) mxyz.append(np.copy(sim.spin)) mxyz = np.array(mxyz) if do_plot: ts_ns = np.array(real_ts) * 1e9 plt.plot(ts_ns, mxyz[:, 0], ".-", label="mx") plt.plot(ts_ns, mxyz[:, 1], ".-", label="my") plt.plot(ts_ns, mxyz[:, 2], ".-", label="mz") plt.plot(ts_ns, mz_ref, "-", label="analytical") plt.xlabel("time (ns)") plt.ylabel("mz") plt.title("integrating a macrospin") plt.legend() plt.savefig("test_llg_stt.png") print(("Deviation = {0}".format(np.max(np.abs(mxyz[:, 2] - mz_ref))))) assert np.max(np.abs(mxyz[:, 2] - mz_ref)) < 1e-9
def test_sim_single_spin_sllg(do_plot=False): mesh = CuboidMesh(nx=1, ny=1, nz=1) sim = Sim(mesh, name='spin', driver='sllg') alpha = 0.1 gamma = 2.21e5 sim.set_options(dt=5e-15, gamma=gamma) sim.alpha = alpha sim.mu_s = 1.0 sim.set_m((1, 0, 0)) H0 = 1e5 sim.add(Zeeman((0, 0, H0))) ts = np.linspace(0, 1e-10, 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) a_mx, a_my, a_mz = single_spin(alpha, gamma, H0, ts) if do_plot: plot(real_ts, mx, my, mz, a_mx, a_my, a_mz, name='spin_sllg.pdf', title='integrating a spin') print(("Max Deviation = {0}".format( np.max(np.abs(mz - a_mz))))) assert np.max(np.abs(mz - a_mz)) < 1e-8
def relax_system(mesh): sim = Sim(mesh, name='relax') sim.alpha = 0.1 sim.set_m(init_m) J = 1 exch = UniformExchange(J) sim.add(exch) dmi = DMI(0.05 * J) sim.add(dmi) ts = np.linspace(0, 1, 11) for t in ts: print t, sim.spin_length() - 1 sim.run_until(t) sim.save_vtk() return sim.spin