Oersted field assisted magnetization reversal in cylindrical core-shell nanostructures

Abstract

A method to manipulate magnetization reversal in core-shell nanostructures is presented. The focus is on cylindrical multilayer structures comprising of an inner conductor wire covered by two shells: (i) an intermediate non-conducting and non-magnetic shell and (ii) a nanotube made of an outer ferromagnetic layer. The properties of the magnetization reversal of the ferromagnetic phase are investigated when a circular Oersted field is generated by applying an electric current through the inner wire. Coercive fields and remanent magnetization as functions of the circular field strength are explored. By means of a simple analytical model and OOMMF simulations, once the current is turned on, two key results have been found: (i) A manipulable axial demagnetization, that is, a magnetization transition from the quasi uniform alignment to a flux closure circular configuration when the circular field strength is above a critical field; and (ii) a quadratic reduction of the coercivity on the circular field strength, in the case that the nanotube magnetization is switched by an applied magnetic field along the tube axis and further assisted by a circular Oersted field. It is found that in this kind of structures, Oersted field assisted magnetization reversal (OAMR) can be an alternative way to reduce coercivity, as required by the magnetic storage industry and currently performed with heat assisted techniques.

Frequency linewidth and decay length of spin waves in curved magnetic membranes

“…The critical field to stabilize the vortex magnetic state is calculated to be µ 0 H crit = µ 0 H u ≈ 5.9 mT. 9 Therefore, a field of µ 0 H 0 = 6 mT is applied to set the circular magnetization state. .…”

“…The critical field to stabilize the vortex magnetic state is calculated to be µ 0 H crit = µ 0 H u ≈ 5.9 mT. 9 Therefore, a field of µ 0 H 0 = 6 mT is applied to set the circular magnetization state. Figure 2 summarizes our results for SWs with the zeroth-order and the first two higher-order modes in terms of the azimuthal wavenumbers n = 0, ±1, ±2.…”

“…For instance, in SW-based logic devices, the asymmetric dispersion relation provides the condition for the unidirectional propagation of SW packages a) Corresponding author: j.otalora@ifw-dresden.de For nanotubes with radii smaller than a critical radius, a circular (azimuthal) magnetic field H0 = H0 φ is required to stabilize this configuration, while the exchange interaction prefers the homogeneous magnetization state along the long axis. The critical magnetic field related to the critical radius can be analytically calculated for a nanotube with specific geometrical and material parameters, as given by Otálora et al 9 . However, for radii above 100 nm, for most of the metallic magnetic materials, the vortex state is the preferred equilibrium configuration.…”

Soliton collisions in soft magnetic nanotube with uniaxial anisotropy

“…The magnetization distribution and domain wall (DW) dynamics in magnetic nanotubes have recently been studied both theoretically [11][12][13][14][15][16][17][18][19] and experimentally [20][21][22][23] . The control of the magnetic domain state and magnetization reversal process in magnetic nanotubes is especially important for various applications.…”

Steady motion of skyrmions and domains walls under diffusive spin torques

“…Above this threshold the profile of the magnetization is no longer rigid and there is a nucleation of more complex DWs such as vortex or antivortex walls. An important aspect in the study of the interaction of current and magnetization is the limited impact of the Oersted field produced by the current in long magnetic stripes [23,[41][42][43], compared to wider geometries such as magnetic disks [44][45][46][47].…”