Magnetoresistance in Hybrid Pt/CoFe2O4 Bilayers Controlled by Competing Spin Accumulation and Interfacial Chemical Reconstruction

TL;DR

This study investigates how interfacial chemical reconstructions and spin accumulation influence magnetoresistance in Pt/CoFe2O4 bilayers, revealing that growth temperature affects interfacial magnetism and the dominant magnetoresistance mechanism.

Contribution

It provides a detailed analysis of the interplay between spin accumulation and interfacial chemistry in controlling magnetoresistance in Pt/CoFe2O4 heterostructures.

Findings

Higher growth temperature induces magnetic moments in Pt due to alloying.

Magnetoresistance can be dominated by either SMR or AMR depending on interface chemistry.

Interfacial chemical reconstruction can be tailored to control magnetoresistance mechanisms.

Abstract

Pure spin currents hold promises for an energy-friendlier spintronics. They can be generated by a flow of charge along a non-magnetic metal having a large spin-orbit coupling. It produces a spin accumulation at its surfaces, controllable by the magnetization of an adjacent ferromagnetic layer. Paramagnetic metals typically used are close to a ferromagnetic instability and thus magnetic proximity effects can contribute to the observed angular-dependent magnetoresistance (ADMR). As interface phenomena govern the spin conductance across the metal/ferromagnetic-insulator heterostructures, unraveling these distinct contributions is pivotal to full understanding of spin current conductance. We report here x-ray absorption and magnetic circular dichroism (XMCD) at Pt-M and (Co,Fe)-L absorption edges and atomically-resolved energy loss electron spectroscopy (EELS) data of Pt/CoFe2O4 bilayers where CoFe2O4 layers have been capped by Pt grown at different temperatures. It turns out that the ADMR differs dramatically, being either dominated by spin Hall magnetoresistance (SMR) associated to spin Hall effect or anisotropic magnetoresistance (AMR). The XMCD and EELS data indicate that the Pt layer grown at room temperature does not display any magnetic moment, whereas when grown at higher temperature it is magnetic due to interfacial Pt-(Co,Fe) alloying. These results allow disentangling spin accumulation from interfacial chemical reconstructions and for tailoring the angular dependent magnetoresistance.