Spin Seebeck effect in magnetic junctions with a compensated ferrimagnet

TL;DR

This paper demonstrates that compensated ferrimagnets can generate robust spin currents via the spin Seebeck effect, offering a stray-field-free spin-current source for spintronics, unlike altermagnets.

Contribution

It introduces a four-sublattice model showing isotropic magnon splitting in compensated ferrimagnets produces significant spin currents, contrasting previous anisotropy-based mechanisms.

Findings

Magnon splitting in compensated ferrimagnets generates a strong spin current.

The spin Seebeck effect vanishes in altermagnet junctions under similar conditions.

Compensated ferrimagnets are suitable for thermal spin-current generation in spintronics.

Abstract

Compensated ferrimagnets enable ferromagnet-like spin transport without net magnetization. We study the spin Seebeck effect in a compensated ferrimagnet/normal-metal junction using a four-sublattice model in which sublattice inequivalence arises from differences in exchange couplings, in contrast to the previously studied anisotropy-based mechanism. Within the nonequilibrium Green's function framework, we show that isotropic magnon splitting generates a robust spin current with a magnitude comparable to that in standard ferromagnetic junctions. We also demonstrate that the spin Seebeck effect vanishes in altermagnet junctions under identical conditions, thereby establishing compensated ferrimagnets as uniquely suited for thermal spin-current generation among magnetically compensated systems. These results provide a theoretical basis for the applications of compensated ferrimagnets with exchange-coupling asymmetry as stray-field-free spin-current sources in spintronic devices.