Anomalous Inverse Spin Hall Effect (AISHE) due to Unconventional Spin Currents in Ferromagnetic Films with Tailored Interfacial Magnetic Anisotropy

TL;DR

This study demonstrates the detection of Anomalous Inverse Spin Hall Effect (AISHE) in ferromagnetic films with tailored interfacial magnetic anisotropy, revealing unconventional spin currents and spin-orbit torque at room temperature.

Contribution

It introduces a novel method to observe AISHE in single-layer ferromagnetic films with engineered magnetic textures, highlighting the role of interfacial anisotropy.

Findings

Detection of harmonic and second harmonic Hall voltages in permalloy films.

Unconventional spin currents induce spin-orbit torque.

Control samples show reduced Hall signals, confirming the model.

Abstract

A single layer ferromagnetic film magnetized in the plane of an ac current flow, exhibits a characteristic Hall voltage with harmonic and second harmonic components, which is attributed to the presence of spin currents with polarization non-collinear with the magnetization. A set of 30 nm thick permalloy (Py) films used in this study are deposited at an oblique angle with respect to the substrate plane which induces an in-plane easy axis in the magnetization of the initial nucleating layers of the films which is distinct from the overall bulk magnetic properties of the film. This unusual magnetic texture provides a platform for the direct detection of inverse spin Hall effect in Hall bar shaped macroscopic devices at room temperatures which we denote as Anomalous Inverse Spin Hall Effect (AISHE). Control samples fabricated by normal deposition of permalloy with slow rotation of substrate shows significant reduction of the harmonic Hall signal that further substantiates the model. The analysis of the second harmonic Hall signal corroborates the presence of spin-orbit torque arising from the unconventional spin-currents in the single-layer ferromagnets.