Microwave directional dichroism resonant with spin excitations in the polar ferromagnet GaV$_4$S$_8$

TL;DR

This study demonstrates significant microwave directional dichroism in GaV$_4$S$_8$, a polar ferromagnet, showing potential for microwave diode applications even in multi-domain samples due to magnetoelectric effects.

Contribution

It reveals large directional dichroism in GaV$_4$S$_8$ caused by spin excitations, applicable to multi-domain crystals, advancing microwave diode technology.

Findings

Directional dichroism up to 20% observed

Distinct magnetic resonance for each domain

Multi-domain samples can function as microwave diodes

Abstract

We have investigated the directional dichroism of magnetic resonance spectra in the polar ferromagnet GaV$_4$S$_8$. While four types of structural domains are energetically degenerated under zero field, the magnetic resonance for each domain is well separated by applying magnetic fields due to uniaxial magnetic anisotropy. Consequently, the directional dichroism as large as 20 % is clearly observed without domain cancellation. The present observation therefore demonstrates that not only magnetoelectric mono-domain crystals but also magnetoelectric multi-domain specimens can be used to realize microwave (optical) diodes owing to the lack of inversion domains.