Magnon hybridization in ferrimagnetic heterostructures

TL;DR

This paper investigates magnon hybridization in ferrimagnetic heterostructures, revealing how localized and extended magnon modes affect thermal and spin Seebeck effects, with implications for tunable spintronic devices.

Contribution

It provides a detailed analysis of magnon mode profiles and predicts how their thermal excitation influences the spin Seebeck effect, including a tunable sign change based on YIG thickness.

Findings

Distinct magnon mode profiles with different polarizations identified

Predicted shift in sign-changing temperature of spin Seebeck effect

Sign-changing point tunable by YIG layer thickness

Abstract

We study magnon hybridization in a ferrimagnetic heterostructure consisting of ultrathin gadolinium iron garnet and yttrium iron garnet layers and show the localized and extended spatial profiles of the magnon modes with different polarizations. These modes are expected to have distinct thermal excitation properties in the presence of a temperature gradient across the heterostructure. From a quantitative analysis of their consequences on longitudinal spin Seebeck effect, we predict an observable shift of the sign-changing temperature with respect to the one previously observed in gadolinium iron garnet. Moreover, the sign-changing point of spin Seebeck signal is found to be tunable by YIG thickness. Our results suggest the necessity of taking into account the temperature difference between the magnon modes in ferrimagnetic heterostructures.