Nutational switching in ferromagnets and antiferromagnets

TL;DR

This paper explores how nutation in magnetization dynamics enables ultrafast spin switching in ferromagnets and antiferromagnets, potentially surpassing traditional precessional methods for data writing.

Contribution

It introduces a theoretical and simulation-based analysis of nutational effects on spin switching, revealing new mechanisms for ultrafast magnetic state control.

Findings

Linearly polarized fields induce 90° switching in ferromagnets.

Circularly polarized fields cause 180° switching via tilting and rotation.

In antiferromagnets, high-frequency fields align the order parameter parallel to the field.

Abstract

It was demonstrated recently that on ultrashort time scales magnetization dynamics does not only exhibit precession but also nutation. Here, we investigate how nutation can contribute to spin switching leading towards ultrafast data writing. We use analytic theory and atomistic spin simulations to discuss the behavior of ferromagnets and antiferromagnets in high-frequency magnetic fields. In ferromagnets, linearly polarized fields align the magnetization perpendicular to the external field, enabling $90^{\circ}$ switching. For circularly polarized fields in the $xy$ plane, the magnetization tilts to the $z$ direction. During this tilting, it rotates around the $z$ axis, allowing $180^{\circ}$ switching. In antiferromagnets, external fields with frequencies higher than the nutation frequency align the order parameter parallel to the field direction, while for lower frequencies it is oriented perpendicular to the field. The switching frequency increases with the magnetic field strength, and it deviates from the Larmor frequency, making it possible to outpace precessional switching in high magnetic fields.