Static magnetic proximity effects and spin Hall magnetoresistance in Pt/Y$_{3}$Fe$_{5}$O$_{12}$ and inverted Y$_{3}$Fe$_{5}$O$_{12}$/Pt bilayers

TL;DR

This study investigates magnetic proximity effects and magnetoresistance in Pt/Y3Fe5O12 bilayers, revealing induced magnetic moments only in inverted layer structures due to intermixing, and distinguishes between spin Hall and anisotropic magnetoresistance contributions.

Contribution

It demonstrates that layer stacking order influences magnetic proximity effects and magnetoresistance, highlighting the role of intermixing at interfaces in Pt/Y3Fe5O12 heterostructures.

Findings

Induced magnetic moments in Pt are observed only in inverted layer structures.

Intermixing at the interface causes the magnetic polarization in Pt.

Complex magnetoresistance arises from superimposed spin Hall and anisotropic effects.

Abstract

The magnetic state of heavy metal Pt thin films in proximity to the ferrimagnetic insulator Y$_{3}$Fe$_{5}$O$_{12}$ has been investigated systematically by means of x-ray magnetic circular dichroism and x-ray resonant magnetic reflectivity measurements combined with angle-dependent magnetotransport studies. To reveal intermixing effects as the possible cause for induced magnetic moments in Pt, we compare thin film heterostructures with different order of the layer stacking and different interface properties. For standard Pt layers on Y$_{3}$Fe$_{5}$O$_{12}$ thin films, we do not detect any static magnetic polarization in Pt. These samples show an angle-dependent magnetoresistance behavior, which is consistent with the established spin Hall magnetoresistance. In contrast, for the inverted layer sequence, Y$_{3}$Fe$_{5}$O$_{12}$ thin films grown on Pt layers, Pt displays a finite induced magnetic moment comparable to that of all-metallic Pt/Fe bilayers. This magnetic moment is found to originate from finite intermixing at the Y$_{3}$Fe$_{5}$O$_{12}$/Pt interface. As a consequence, we found a complex angle-dependent magnetoresistance indicating a superposition of the spin Hall and the anisotropic magnetoresistance in these type of samples. Both effects can be disentangled from each other due to their different angle dependence and their characteristic temperature evolution.