Dynamic detection of current-induced spin-orbit magnetic fields: a phase independent approach

TL;DR

This paper introduces a phase-independent, self-calibrated method using time-resolved magneto-optic Kerr microscopy to measure current-induced spin-orbit magnetic fields in ferromagnet/semiconductor heterostructures by analyzing standing spin wave patterns.

Contribution

A novel, phase-independent approach to determine spin-orbit fields through magnetization dynamics analysis, applicable to various material systems.

Findings

Successfully measured spin-orbit fields in Fe/GaAs heterostructures.

Differentiated spin-orbit fields from Oersted fields via mode pattern analysis.

Method is adaptable to other ferromagnetic heterostructures.

Abstract

Current induced spin-orbit torques (SOTs) in ferromagnet/non-magnetic metal heterostructures open vast possibilities to design spintronic devices to store, process and transmit information in a simple architecture. It is a central task to search for efficient SOT-devices, and to quantify the magnitude as well as the symmetry of current-induced spin-orbit magnetic fields (SOFs). Here, we report a novel approach to determine the SOFs based on magnetization dynamics by means of time-resolved magneto-optic Kerr microscopy. A microwave current in a narrow Fe/GaAs (001) stripe generates an Oersted field as well as SOFs due to the reduced symmetry at the Fe/GaAs interface, and excites standing spin wave (SSW) modes because of the lateral confinement. Due to their different symmetries, the SOFs and the Oersted field generate distinctly different mode patterns. Thus it is possible to determine the magnitude of the SOFs from an analysis of the shape of the SSW patterns. Specifically, this method, which is conceptually different from previous approaches based on lineshape analysis, is phase independent and self-calibrated. It can be used to measure the current induced SOFs in other material systems, e.g., ferromagnetic metal/non-magnetic metal heterostructures.