FMR-related phenomena in spintronic devices

TL;DR

This review discusses the use of spin transfer torque ferromagnetic resonance (ST-FMR) techniques to evaluate spin-orbit torque efficiency in various spintronic materials, highlighting experimental setups, data analysis, and recent research findings.

Contribution

It provides a comprehensive overview of ST-FMR measurement methods and their application across diverse materials in spintronics, emphasizing recent advances and challenges.

Findings

ST-FMR is a versatile method for measuring SOT efficiency.

Different materials exhibit varied SOT behaviors and efficiencies.

The review identifies key trends and future directions in spintronic research.

Abstract

Spintronic devices, such as non-volatile magnetic random access memories and logic devices, have attracted considerable attention as potential candidates for future high efficient data storage and computing technology. In a heavy metal or other emerging material with strong spin-orbit coupling (SOC), the charge currents induce spin currents or spin accumulations via SOC. The generated spin currents can exert spin-orbit torques (SOTs) on an adjacent ferromagnet, which opens up a new way to realize magnetization dynamics and switching of the ferromagnetic layer for spintronic devices. In the SOT scheme, the charge-to-spin interconversion efficiency (SOT efficiency) is an important figure of merit for applications. For the effective characterization of this efficiency, the ferromagnetic resonance (FMR) based methods, such as the spin transfer torque ferromagnetic resonance (ST-FMR) and the spin pumping, are common utilized in addition to low frequency harmonic or dc measurements. In this review, we focus on the ST-FMR measurements for the evaluation of the SOT efficiency. We provide a brief summary of the different ST-FMR setups and data analysis methods. We then discuss ST-FMR and SOT studies in various materials, including heavy metals and alloys, topological insulators, two dimensional (2D) materials, interfaces with strong Rashba effect, antiferromagnetic materials, two dimensional electron gas (2DEG) in oxide materials and oxidized nonmagnetic materials.