Magnetization switching by microwaves initially rotating in opposite direction to precession

TL;DR

This paper demonstrates that microwaves initially rotating opposite to magnetization precession can more efficiently induce magnetization switching when their frequency varies with time, challenging conventional understanding.

Contribution

It introduces a new mechanism for microwave-assisted magnetization reversal using opposite rotation microwaves with time-dependent frequency, supported by analytical and numerical evidence.

Findings

Opposite rotation microwaves destabilize magnetization at equilibrium.

Time-dependent frequency enhances switching efficiency.

Numerical simulations confirm the proposed switching mechanism.

Abstract

A common understanding of magnetization switching in microwave-assisted magnetization reversal is that the rotation direction of the microwaves should be the same with the precession direction of the magnetization. In this letter however, we show that microwaves initially rotating opposite to the magnetization precession destabilize the magnetization at an equilibrium and induces the switching more efficiently, when the microwave frequency depends on time. This argument is analytically deduced from energy balance equation. We also establish a model satisfying this condition, and confirm magnetization switching solely by microwaves by using numerical simulation.