Giant Anomalous Hall Conductivity at the Pt/Cr 2 O 3 Interface

Abstract

The interface between a magnetic material and a heavy metal that has a large spin-orbit interaction is at the root of various spin-related phenomena. In this paper, we address the peculiar spin-dependent transport at a $\mathrm{Pt}/{\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$ interface by exploring the origin of the nonlinear anomalous Hall effect (AHE) in $\mathrm{Pt}/{\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$ bilayers. X-ray magnetic circular dichroism (XMCD) measurements show no appreciable magnetic moment at the interface originating from $\mathrm{Cr}$ 3d and $\mathrm{Pt}$ 5d orbitals, which could be associated with the AHE response. A possible interfacial magnetic moment M at the $\mathrm{Pt}/{\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$ interface, assumed from the detection limit of the XMCD measurements, yields an anomalous Hall conductivity ($\ensuremath{\sigma}\mathrm{AHE}$) per unit net magnetic moment (M), \ensuremath{-}${\ensuremath{\sigma}}_{\mathrm{AHE}}$/M, of 0.57 ${\mathrm{V}}^{\ensuremath{-}1}$, which is extraordinary large compared with that for general magnetic materials. Together with first-principles calculations, the results suggest the possibility of an intrinsic AHE in the $\mathrm{Pt}/{\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$ interface that does not rely on the net magnetic moment.