Fast magnetization reversal of a magnetic nanoparticle induced by cosine chirp microwave field pulse

TL;DR

This study demonstrates that a circularly polarized cosine chirp microwave pulse can efficiently induce rapid magnetization reversal in magnetic nanoparticles, potentially enabling fast, low-cost memory devices.

Contribution

It introduces the use of cosine chirp microwave pulses for fast, energy-efficient magnetization reversal, showing advantages over linear chirp pulses and highlighting optimal conditions.

Findings

CCMP achieves faster reversal with lower amplitude and frequency than linear chirp.

Enhanced shape anisotropy reduces microwave requirements.

Optimal Gilbert damping improves reversal speed.

Abstract

We investigate the magnetization reversal of single-domain magnetic nanoparticle driven by the circularly polarized cosine chirp microwave pulse (CCMP). The numerical findings, based on the Landau-Lifshitz-Gilbert equation, reveal that the CCMP is by itself capable of driving fast and energy-efficient magnetization reversal. The microwave field amplitude and initial frequency required by a CCMP are much smaller than that of the linear down-chirp microwave pulse. This is achieved as the frequency change of the CCMP closely matches the frequency change of the magnetization precession which leads to an efficient stimulated microwave energy absorption (emission) by (from) the magnetic particle before (after) it crosses over the energy barrier. We further find that the enhancement of easy-plane shape anisotropy significantly reduces the required microwave amplitude and the initial frequency of CCMP. We also find that there is an optimal Gilbert damping for fast magnetization reversal. These findings may provide a pathway to realize the fast and low-cost memory device.