from nsim.model import Value ps = SI(1e-12, "s"); nm = SI(1e-9, "m") # Useful definitions theta_rad = 3.141592654 phi_rad = 1.570796327 #length, width, thick = (2*nm, 16*nm, 64*nm) # System geometry current_density = SI( 100e10, "A/m^2") # Applied current Happ_dir = [0, 0, 0] # Applied field (mT)- # Material definition anis = cubic_anisotropy(axis1=[1, 0, 0], axis2=[0,1,0], K1=SI(-1e4, "J/m^3")) mat = MagMaterial("Co", Ms=SI(9.0e5, "A/m"), exchange_coupling=SI(2.0e-11, "J/m"), llg_gamma_G=SI(2.3245e5, "m/s A"),
if not os.path.exists(mesh_filename): netgen_mesh_from_file(mesh_geo, mesh_filename) relaxed_m = "m0.h5" film_centre = (5, 50, 50) do_relaxation = not os.path.exists(relaxed_m) ps = SI(1e-12, "s") mat = MagMaterial("Py", Ms=SI(0.86e6, "A/m"), exchange_coupling=SI(13e-12, "J/m"), llg_damping=SI(0.5 if do_relaxation else 0.01)) mat.sl_P = 0.0 if do_relaxation else 0.4 # Polarisation mat.sl_d = SI(3e-9, "m") # Free layer thickness sim = Simulation(do_sl_stt=True) sim.load_mesh(mesh_filename, [("region1", mat)], unit_length=SI(1e-9, "m")) def m0(r): dx, dy, dz = tuple(ri - ri0*1e-9 for ri, ri0 in zip(r, film_centre)) v = (1.0e-9, dz, -dy) vn = (1.0e-9**2 + dy*dy + dz*dz)**0.5 return tuple(vi/vn for vi in v) sim.set_m(m0) sim.set_H_ext([0, 0, 0], SI("A/m"))
# Applied field Happ_dir = [0, 0, 10] # in mT # Material definition mat = MagMaterial("Py", Ms=SI(860e3, "A/m"), exchange_coupling=SI(13e-12, "J/m"), llg_gamma_G=SI(221017, "m/s A"), llg_damping=SI(0.014)) # Parameters relevant to spin-torque transfer # Current and Current Density I = SI(5e-5, "A") J = I / (length * width) mat.sl_P = 0.4 # Polarisation mat.sl_lambda = 2.0 # lambda parameter mat.sl_d = height # Free layer thickness # Direction of the polarisation theta = 40.0 phi = 90.0 theta_rad = math.pi * theta / 180.0 phi_rad = math.pi * phi / 180.0 P_direction = [ math.sin(theta_rad) * math.cos(phi_rad), math.sin(theta_rad) * math.sin(phi_rad), math.cos(theta_rad) ] sim = Simulation(do_sl_stt=True, do_demag=False)
# create mesh if required if not os.path.exists(mesh_filename): netgen_mesh_from_file(mesh_geo, mesh_filename) relaxed_m = "m0.h5" film_centre = (5, 50, 50) do_relaxation = not os.path.exists(relaxed_m) ps = SI(1e-12, "s") mat = MagMaterial("Py", Ms=SI(0.86e6, "A/m"), exchange_coupling=SI(13e-12, "J/m"), llg_damping=SI(0.5 if do_relaxation else 0.01)) mat.sl_P = 0.0 if do_relaxation else 0.4 # Polarisation mat.sl_d = SI(10e-9, "m") # Free layer thickness sim = Simulation(do_sl_stt=True) sim.load_mesh(mesh_filename, [("region1", mat)], unit_length=SI(1e-9, "m")) def m0(r): dx, dy, dz = tuple(ri - ri0 * 1e-9 for ri, ri0 in zip(r, film_centre)) v = (1.0e-9, dz, -dy) vn = (1.0e-9**2 + dy * dy + dz * dz)**0.5 return tuple(vi / vn for vi in v) sim.set_m(m0)
mesh_geo = \ ("algebraic3d\n" "solid cube = orthobrick (0, 0, 0; %s, %s, %s) -maxh = 2.5;\n" "tlo cube;\n" % tuple(map(lambda x: float(x/nm), (length, width, thick)))) netgen_mesh_from_string(mesh_geo, mesh_filename, keep_geo=True) # Material definition anis = uniaxial_anisotropy(axis=[0, 0, 1], K1=-SI(0.1e6, "J/m^3")) mat = MagMaterial("Py", Ms=SI(860e3, "A/m"), exchange_coupling=SI(13e-12, "J/m"), llg_gamma_G=SI(221017, "m/s A"), llg_damping=SI(0.014), anisotropy=anis) mat.sl_P = 0.4 # Polarisation mat.sl_lambda = 2.0 # lambda parameter mat.sl_d = SI(5.0e-9, "m") # Free layer thickness sim = Simulation(do_sl_stt=True, do_demag=False) sim.load_mesh(mesh_filename, [("region1", mat)], unit_length=nm) sim.set_m([1, 0.01, 0.01]) sim.set_H_ext(Happ_dir, 0.001*Tesla/mu0) # Direction of the polarization theta_rad = math.pi*theta/180.0 phi_rad = math.pi*phi/180.0 P_direction = [math.sin(theta_rad)*math.cos(phi_rad), math.sin(theta_rad)*math.sin(phi_rad), math.cos(theta_rad)]