Single femtosecond laser pulse-driven ferromagnetic switching

TL;DR

This paper demonstrates that single femtosecond laser pulses can coherently switch the magnetization of ferromagnetic materials through thermal anisotropy torque, enabling fast, energy-efficient, and scalable magnetic memory applications.

Contribution

It introduces a novel method for deterministic single-pulse magnetization switching in ferromagnets, overcoming previous limitations associated with ferrimagnetic materials.

Findings

Robust toggle switching over femtoseconds to picoseconds pulse durations

Reproducible switching in CoFeB/MgO magnetic tunnel junctions with high magnetoresistance

Energy-efficient switching at 17 fJ per 100-nm bit

Abstract

Light pulses offer a faster, more energy-efficient, and direct route to magnetic bit writing, pointing toward a hybrid memory and computing paradigm based on photon transmission and spin retention. Yet progress remains hindered, as deterministic, single-pulse optical toggle switching has so far been achieved only with ferrimagnetic materials, which require too specific a rare-earth composition and temperature conditions for technological use. In mainstream ferromagnet--central to spintronic memory and storage--such bistable switching is considered fundamentally difficult, as laser-induced heating does not inherently break time-reversal symmetry. Here, we report coherent magnetization switching in ferromagnets, driven by thermal anisotropy torque with single laser pulses. The toggle switching behavior is robust over a broad range of pulse durations, from femtoseconds to picoseconds, a prerequisite for practical applications. Furthermore, the phenomenon exhibits reproducibility in CoFeB/MgO-based magnetic tunnel junctions with a high magnetoresistance exceeding 110%, as well as the scalability down to nanoscales with remarkable energy efficiency (17 fJ per 100-nm-sized bit). These results mark a notable step toward integrating opto-spintronics into next-generation memory and storage technologies.