# Spin-orbit torques and their associated effective fields from gigahertz to terahertz

## TL;DR

This paper explores the high-frequency behavior of spin-orbit torques in spintronics, revealing their frequency-independent effective fields up to terahertz frequencies, which could enable faster, energy-efficient magnetic devices.

## Contribution

It provides the first realistic material-specific analysis of the dynamical transverse and longitudinal components of spin-orbit torques at terahertz frequencies.

## Key findings

- Effective magnetic fields are frequency-independent up to terahertz frequencies.
- Dynamical regimes significantly alter the transverse spin-orbit torques.
- Longitudinal torque components can change the magnetic moment's magnitude.

## Abstract

Terahertz spintronics offers the prospect of devices which are both faster and more energy-efficient. A promising route to achieve this goal is to exploit current-induced spin-orbit torques. However, the high-frequency properties of these quantities remain unexplored both experimentally and theoretically, within a realistic material-specific approach. Here we investigate the dynamical transverse components of the torques and uncover contributions longitudinal to the magnetic moment capable of changing its magnitude. We show that, while the torques can be drastically altered in the dynamical regime, the effective magnetic fields that accompany them present a frequency-independent behaviour, ranging from the static limit up to the terahertz domain - including the ferromagnetic resonance of the system. The outcomes of this work point to new ways to control magnetic units in next-generation spintronic devices.