Microwave non-reciprocity of magnon excitations in a non-centrosymmetric antiferromagnet Ba$_2$MnGe$_2$O$_7$

TL;DR

This study investigates microwave non-reciprocity in a non-centrosymmetric antiferromagnet, Ba$_2$MnGe$_2$O$_7$, confirming magnon modes and explaining non-reciprocity through spin wave theory and Kubo formula.

Contribution

First experimental observation of microwave non-reciprocity in Ba$_2$MnGe$_2$O$_7$ and analysis of its origin using spin wave theory and Kubo formula.

Findings

Magnon modes match spin wave theory predictions

Microwave non-reciprocity observed in one mode

Exchange interaction and anisotropy parameters determined

Abstract

We have investigated the microwave non-reciprocity for a non-centrosymmetric antiferromagnet Ba$_2$MnGe$_2$O$_7$. The magnon modes expected by the conventional spin wave theory for staggered antiferromagnets are certainly observed. The magnitudes of exchange interaction and magnetic anisotropy are obtained by the comparison with the theory. The microwave non-reciprocity is identified for one of these mode. The relative magnitude of microwave non-reciprocity can be explained with use of spin wave theory and Kubo formula.