Magnon Characteristics in Metallic Bilayers through Unidirectional Magnetoresistance

Abstract

Magnon, quasi-particles arising from collective mode of spin excitations in magnetic materials, play an important role in understanding many spin-related phenomena, such as ultrafast spin dynamics and current-induced magnetic auto-oscillation. In particular, the concept of magnon current has been proposed as a potential replacement for electronic systems, offering data technology solutions without Joule heating-induced power dissipation. Therefore, the identification of magnon characteristics is highly demanded for realizing future magnonic applications. In this study, we investigate magnon characteristics in metallic bilayers using unidirectional magnetoresistance (UMR), a magnon-related phenomenon observed in ferromagnet/heavy metal bilayer structures. Through experiments focused on crystallographic dependence and non-local UMR measurement configurations, our results demonstrate that magnon can be efficiently generated in a system with I-sing type exchange interaction and the high energy magnons are much more efficient for spin pumping and spin current generation. Our results shed light on the underlying mechanism of energy-dependent magnonic phenomena and suggest a route to enhance the efficiency of magnon generation in the magnonic devices.