Chiral spin-wave velocities induced by all-garnet interfacial Dzyaloshinskii-Moriya interaction in ultrathin yttrium iron garnet films

TL;DR

This study experimentally demonstrates interfacial Dzyaloshinskii-Moriya interaction in ultrathin yttrium iron garnet films by measuring nonreciprocal spin wave velocities, revealing a chiral velocity behavior crucial for chiral magnonics.

Contribution

First experimental evidence of interfacial DMI in ultrathin YIG films using electrical spectroscopy and velocity measurements, highlighting its interface origin and potential for low-damping chiral magnonics.

Findings

DMI constant of 16 μJ/m² measured in YIG films

Chirality observed in spin wave velocities related to DMI

DMI originates from the oxide interface between YIG and substrate

Abstract

Spin waves can probe the Dzyaloshinskii-Moriya interaction (DMI) which gives rise to topological spin textures, such as skyrmions. However, the DMI has not yet been reported in yttrium iron garnet (YIG) with arguably the lowest damping for spin waves. In this work, we experimentally evidence the interfacial DMI in a 7~nm-thick YIG film by measuring the nonreciprocal spin wave propagation in terms of frequency, amplitude and most importantly group velocities using all electrical spin-wave spectroscopy. The velocities of propagating spin waves show chirality among three vectors, i.e. the film normal direction, applied field and spin-wave wavevector. By measuring the asymmetric group velocities, we extract a DMI constant of 16~$\mu$J/m$^{2}$ which we independently confirm by Brillouin light scattering. Thickness-dependent measurements reveal that the DMI originates from the oxide interface between the YIG and garnet substrate. The interfacial DMI discovered in the ultrathin YIG films is of key importance for functional chiral magnonics as ultra-low spin-wave damping can be achieved.