Abnormal anomalous Hall effect in permalloy thin film driven by an adjacent silicon oxide layer

Abstract

Abstract We report that the unusual behavior of anomalous Hall effect (AHE) in permalloy (Fe20Ni80, Py) thin film with silicon oxide (SiO2) as an adjacent layer. It is found that sign of AHE changes from positive to negative with decrement in thickness of Py. Through the AHE measurement, we demonstrate that this unusual behavior originates from the interface of Py/SiO2 rather from the structural inversion asymmetry. In the Pt/YIG/Cu/Py/SiO2 multilayer structure with a charge current injected in the Py layer, the information on spin accumulation at the YIG/Cu interface induced by the AHE in Py, can be obtained from the nonlocal voltage measured in the Pt layer. Through the nonlocal measurement, it is found, however, the electrons with same spin for interfacial Py near the SiO2 layer and bulk Py are scattered to the same direction. Hence we can deduce that the sign of spin polarization of the conductivity closely related to the asymmetry in density of states at the Fermi level for interfacial Py and bulk Py should be opposite to each other, which is responsible for the abnormal AHE observed. Our results demonstrate that oxide layer can drive the change of sign of AHE of Py, which provide an alternative way of manipulating the spin-related transport.