Static magnetic proximity effects and spin Hall magnetoresistance in Pt/Y₃ Fe₅ O₁₂ and inverted Y₃ Fe₅ O₁₂/Pt bilayers

Abstract

The magnetic state of heavy metal Pt thin films in proximity to the ferrimagnetic insulator Y3Fe5O12 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 orders of the layer stacking and different interface properties. For standard Pt layers on Y3Fe5O12 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, Y3Fe5O12 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 Y3Fe5O12/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 types of samples. Both effects can be disentangled from each other due to their different angle dependence and their characteristic temperature evolution.