The sign reversal of anomalous Hall effect derived from the transformation of scattering effect in cluster-assembled Ni0.8Fe0.2 nanostructural films

Abstract

Both surface and interface scattering induced a sign reversal of the anomalous Hall effect (AHE) in a few heterostructures. The sign reversal existing in a single substance can clarify the role of the surface scattering in the AHE. Here, cluster-assembled Ni_0.8Fe_0.2 single-substance films prepared by low-energy cluster beam deposition greatly improved the surface effect with cluster size below a characteristic size of 16.17 nm (d_c) due to the high surface-to-volume ratio of the clusters and the loose structure of the films. The films presented a sign reversal of AHE and unusual transitional behavior in temperature- and size-dependent anomalous Hall resistivity with d_c as the critical size. Interestingly, we also observed the sign reversal in the same film with a cluster size of d_c by regulating the temperature. Based on the existing and modified scaling laws, we discovered the transformation between the bulk and surface scattering mechanisms and their coexistence, and both the sign reversal of AHE and the unusual transitional behaviors of anomalous Hall resistivity were attributed to the predominant scattering effects. Temperature- and size-dependent magnetoresistance (MR) also displayed a significant transformation at d_c and further confirm the transitional mechanisms of AHE. This work provides an effective method for regulating AHE to promote its application in spintronic nano-devices.