Interlayer Couplings Mediated by Antiferromagnetic Magnons

TL;DR

This paper investigates how antiferromagnetic magnons mediate interlayer coupling in trilayers, revealing temperature-dependent exchange interactions and anisotropy effects that could be experimentally observed.

Contribution

It introduces a theoretical framework for magnon-mediated interlayer coupling in AF-based trilayers, highlighting temperature and thickness dependencies.

Findings

Exchange interaction is antiferromagnetic at low temperatures.

Exchange interaction becomes ferromagnetic at high temperatures.

Magnitudes of coupling are in the range of 10-100 μeV for nanoscale separations.

Abstract

Collinear antiferromagnets (AFs) support two degenerate magnon excitations carrying opposite spin polarizations, by which magnons can function as electrons in various spin-related phenomena. In an insulating ferromagnet(F)/AF/F trilayer, we explore the magnon-mediated interlayer coupling by calculating the magnon thermal energy in the AF as a function of the orientations of the Fs. The effect manifests as an interlayer exchange interaction and a perpendicular magnetic anisotropy; they both depend on temperature and the AF thickness. In particular, the exchange interaction turns out to be antiferromagnetic at low temperatures and ferromagnetic at high temperatures, whose magnitude can be $10-100$ $\mu$eV for nanoscale separations, allowing experimental verification.