Unveiling the role of temperature in sign reversal of anomalous Hall resistivity in epitaxial Pt(3 nm)/Fe4N(≤6 nm)/MgO heterostructures toward spintronic devices

Abstract

The interested anomalous Hall effect (AHE) that occurs in heavy nonmagnetic metal/ferromagnetic metal systems holds immense promise for AHE-based spintronic devices design. However, the mechanisms are still under debate due to the complicated interfacial spin–orbit coupling (SOC) effects. Here, the electronic transport properties of Pt (tPt ≤ 6 nm)/Fe4N (tFe4N ≤ 6 nm)/MgO(sub.) heterostructures were investigated. The sign reversal of Hall resistivity ρxy occurs in ultrathin Pt/Fe4N bilayers. The dependence between AHE resistivity ρAH and temperature T changes from ρAH∝T to ρAH∝−T with decreasing Fe4N thickness from 6 to 3 nm in Pt(3 nm)/Fe4N(t nm) (t =6, 5, 4, and 3). Meanwhile, a critical transition temperature Tc appears in Pt (3 nm)/Fe4N (t ≤ 5 nm). The changes from ρxy∝T to ρxy∝−T and the appearance of Tc can be ascribed to the contributions to AHE from the magnetic proximity effect (MPE) and inverse spin Hall effect (ISHE). ρxy induced by MPE increases with increasing temperature, while ρxy caused by ISHE decreases with increasing temperature in Pt (3 nm)/Fe4N (t ≤ 6 nm). Our work demonstrates that the effects of interfacial SOC on AHE unveil the role of temperature in the sign reversal of ρxy, which provides a tunable platform for the development of AHE-based spintronic devices by enabling reversible control of Hall response through thermal modulation.