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

Abstract

We report numerical and analytical studies of the reversal of the magnetic moment of a singledomain 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 α. It is shown that the most efficient magnetization reversal requires a non-linear time dependence of the frequency, ω(t), for which an exact analytical formula is derived with account of damping. The necessary condition of the reversal is h > αd. 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.

Autoresonant switching of the magnetization in single-domain nanoparticles: Two-level theory

“…This phenomenon has been observed in atomic systems [18,19], plasmas [20,21], fluids [22], and semiconductor quantum wells [23]. Some earlier numerical and analytical studies [24][25][26] pointed out the efficiency of a chirped microwave field to induce the reversal of the magnetic moment in a nanoparticle, but did not exploit the analytical tools provided by the autoresonance theory.…”

Autoresonant control of the magnetization switching in single-domain nanoparticles

“…Some authors also noticed the beneficial effect of a chirped pulse on the magnetization dynamics in a nanoparticle [24][25][26], but lacked the analytical tools provided by the autoresonance theory. The autoresonance theory was used in the past to study the excitation of high-amplitude magnetization precession in ferromagnetic thin films [27] and the dynamics of localized magnetic inhomogeneities in a ferromagnet [28].…”

Switching of magnetic moments of nanoparticles by surface acoustic waves

“…It is well known that such ac fields are sufficient to reverse magnetic moments through consecutive absorption of photons of spin 1, see Ref. 24 of the manuscript and references therein. In our case the surface phonons get consecutively absorbed by the magnetic moment, not the photons.…”