Phase reciprocity of spin-wave excitation by a microstrip antenna

TL;DR

This study investigates the phase relationship of counterpropagating spin waves excited by a microstrip antenna in yttrium iron garnet films, revealing phase symmetry in surface waves and phase difference in volume waves, supported by experimental and theoretical analysis.

Contribution

It demonstrates the phase reciprocity of spin-wave excitation by a microstrip antenna and distinguishes behavior between reciprocal and non-reciprocal spin waves.

Findings

Backward volume magnetostatic spin waves show a π phase difference.

Magnetostatic surface spin waves preserve phase symmetry.

Experimental results are supported by theoretical analysis.

Abstract

Using space-, time- and phase-resolved Brillouin light scattering spectroscopy we investigate the difference in phase of the two counterpropagating spin waves excited by the same microwave microstrip transducer. These studies are performed both for backward volume magnetostatic waves and magnetostatic surface waves in an in-plane magnetized yttrium iron garnet film. The experiments show that for the backward volume magnetostatic spin waves (which are reciprocal and excited symmetrically in amplitude) there is a phase difference of $\pi$ associated with the excitation process and thus the phase symmetry is distorted. On the contrary, for the magnetostatic surface spin waves (which are non-reciprocal and unsymmetrical in amplitude) the phase symmetry is preserved (there is no phase difference between the two waves associated with the excitation). Theoretical analysis confirms this effect.