Thermal generation of spin current in epitaxial CoFe2O4 thin films

TL;DR

This study investigates the longitudinal spin Seebeck effect in epitaxial CoFe2O4 thin films, demonstrating thermally generated spin currents detectable via inverse spin Hall effect, with temperature-dependent behavior revealing magnon contributions and magnetic anisotropy insights.

Contribution

It provides the first detailed analysis of the LSSE in epitaxial CFO thin films, highlighting the effects of temperature and strain on spin current generation.

Findings

LSSE signal increases linearly with temperature gradient

LSSE coefficient is approximately 100 nV/K at room temperature

Significant reduction of LSSE at low temperatures due to fewer magnons

Abstract

The longitudinal spin Seebeck effect (LSSE) has been investigated in high-quality epitaxial CoFe2O4 (CFO) thin films. The thermally excited spin currents in the CFO films are electrically detected in adjacent Pt layers due to the inverse spin Hall effect (ISHE). The LSSE signal exhibits a linear increase with increasing temperature gradient, yielding a LSSE coefficient of ~100 nV/K at room temperature. The temperature dependence of the LSSE is investigated from room temperature down to 30 K, showing a significant reduction at low temperatures, revealing that the total amount of thermally generated magnons decreases. Furthermore, we demonstrate that the spin Seebeck effect is an effective tool to study the magnetic anisotropy induced by epitaxial strain, especially in ultrathin films with low magnetic moments.