Reversal of magnetization of a single-domain magnetic particle by the ac field of time-dependent frequency

TL;DR

This paper investigates how a circularly polarized ac magnetic field with a time-dependent frequency can reverse the magnetization of a single-domain particle, providing analytical and numerical insights into optimal conditions and potential applications.

Contribution

It introduces a novel approach using time-dependent frequency sweeps for magnetization reversal, including an exact analytical formula accounting for damping effects.

Findings

Reversal efficiency depends on frequency sweep rate, field amplitude, anisotropy, and damping.

Non-linear frequency variation enhances reversal effectiveness.

Proposed a small-scale magnetization reversal device using superconducting links.

Abstract

We report numerical and analytical studies of the reversal of the magnetic moment of a single-domain magnetic particle by a circularly polarized ac field of time-dependent frequency. For the time-linear frequency sweep, the phase diagrams are computed that illustrate the dependence of the reversal on the frequency sweep rate v, the amplitude of the ac field h, the magnetic anisotropy field d, and the damping parameter alpha. It is shown that the most efficient magnetization reversal requires a non-linear time dependence of the frequency, omega(t), for which an exact analytical formula is derived with account of damping. The necessary condition of the reversal is h > alpha d. Implementation of a small-scale magnetization reversal is proposed in which a nanomagnet is electromagnetically coupled to two weak superconducting links controlled by the voltage. Dynamics of such a system is analyzed with account of the back effect of the magnet on the superconducting links.