Anomalous Hall effect in magnetic insulator heterostructures: Contributions from spin-Hall and magnetic-proximity effects

Abstract

In this letter, we study the origin of the anomalous Hall effect (AHE) in ferrimagnetic insulator ${\mathrm{Tm}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$ (TmIG)/Pt heterostructures. A monotonic decrease of the anomalous Hall resistivity ($\mathrm{\ensuremath{\Delta}}{\ensuremath{\rho}}_{\mathrm{AHE}}$) with decreasing temperature is observed for TmIG/Pt, and a sign reversal of $\mathrm{\ensuremath{\Delta}}{\ensuremath{\rho}}_{\mathrm{AHE}}$ occurs at around 80 K. With the addition of a Cu interlayer, the $\mathrm{\ensuremath{\Delta}}{\ensuremath{\rho}}_{\mathrm{AHE}}$ similarly decreases as a function of temperature, but maintains the same sign across the full temperature range. This indicates that both the magnetic-proximity effect and spin Hall effect in the TmIG/Pt bilayer contribute to the AHE signal with opposing signs. The spin-Hall contribution to the AHE is dominant at room temperature but decreases with decreasing temperature. Meanwhile, the magnetic-proximity contribution to the AHE becomes dominant with decreasing temperatures, leading to a change of sign for $\mathrm{\ensuremath{\Delta}}{\ensuremath{\rho}}_{\mathrm{AHE}}$. We exclude a dominant influence of a ferrimagnetic compensation point in the temperature region by complementary magnetic hysteresis and neutron diffraction measurements. Our work, based on a simple method, sheds light on the origin of the AHE in magnetic insulator heterostructures, where the competition between the magnetic-proximity effect and spin Hall effect governs the sign and amplitude of the AHE.