Absence of magnetic proximity effects in magnetoresistive Pt/CoFe2O4 hybrid interfaces

TL;DR

This study investigates magnetoresistance in Pt/CoFe2O4 interfaces and finds no evidence of induced magnetic moments in Pt, suggesting spin-orbit effects are responsible for magnetoresistance rather than magnetic proximity effects.

Contribution

The paper provides direct experimental evidence that magnetic proximity effects are absent in Pt/CoFe2O4 interfaces, highlighting the role of spin-orbit effects in magnetoresistance.

Findings

No detectable magnetic moments in Pt (< 0.001 μB/Pt)

Magnetoresistance not due to proximity-induced magnetism

Spin disorder in CoFe2O4 may influence magnetoresistance behavior

Abstract

Ultra-thin Pt films grown on insulating ferrimagnetic CoFe2O4 (111) epitaxial films display a magnetoresistance upon rotating the magnetization of the magnetic layer. We report here X-ray magnetic circular dichroism (XMCD) recorded at Pt-L2,3 and Pt-M3 edges. The results indicate that the Pt magnetic moment, if any, is below the detection limit (< 0.001 {\mu}$_B$/Pt), thus strongly favoring the view that the presence of CoFe2O4 does not induce the formation of magnetic moments in Pt. Therefore, the observed magnetoresistance cannot be attributed to some sort of proximity-induced magnetic moments at Pt ions and subsequent magnetic-field dependent scattering. It thus follows that either bulk (spin Hall and Inverse spin Hall Effects) or interface (Rashba) spin-orbit related effects dominate the observed magnetoresistance. Furthermore, comparison of bulk magnetization and XMCD data at (Fe,Co)-L2,3 edges suggests the presence of some spin disorder in the CoFe2O4 layer which may be relevant for the observed anomalous non-saturating field-dependence of spin Hall magnetoresistance.