Scaling of the thermally induced sign inversion of longitudinal spin Seebeck effect in a compensated ferrimagnet: Role of magnetic anisotropy

TL;DR

This study investigates how magnetic anisotropy influences the sign and magnitude of the longitudinal spin Seebeck effect in GdIG/Pt films, revealing universal scaling behavior and the potential for tuning LSSE via anisotropy control.

Contribution

It demonstrates the role of magnetic anisotropy and easy axis orientation in the sign inversion and scaling of the LSSE in compensated ferrimagnets, with experimental evidence across different film thicknesses and substrates.

Findings

LSSE signal flips sign below T_Comp in all films.

Universal scaling behavior of LSSE near T_Comp.

Magnetic easy axis orientation affects LSSE signal magnitude and sign.

Abstract

We report on a systematic investigation of the longitudinal spin Seebeck effect (LSSE) in a GGG(Gd3Ga5O12)/GdIG(Gd3Fe5O12)/Pt film series exhibiting an in-plane magnetic easy axis with a compensation temperature (T_Comp) that decreases from 270 to 220 K when decreasing GdIG film thickness from 272 to 31 nm, respectively. For all the films, the LSSE signal flips its sign below T_Comp. We demonstrate a universal scaling behavior of the temperature dependence of LSSE signal for our GdIG films around their respective T_Comp. Additionally, we demonstrate LSSE in a 31 nm GdIG film grown on a lattice-mismatched GSGG (Gd3Sc2Ga3O12) substrate that exhibits an out-of-plane magnetic easy axis at room temperature. However, this sample reveals a spin reorientation transition where the magnetic easy axis changes its orientation to in-plane at low temperatures. We observed a clear distinction in the LSSE signal for the GSGG/GdIG(31 nm)/Pt heterostructure, relative to GGG/GdIG(31nm)/Pt showing an in-plane magnetic easy axis. Our findings underscore a strong correlation between the LSSE signal and the orientation of magnetic easy axis in compensated ferrimagnets and opens the possibility to tune LSSE through effective anisotropy.