Switching ferromagnetic spins by an ultrafast laser pulse: Emergence of giant optical spin-orbit torque

TL;DR

This paper demonstrates that optical spin-orbit torque can switch ferromagnetic spins rapidly using ultrafast laser pulses, potentially revolutionizing magnetic data storage and spintronics with high-speed, efficient, all-optical control.

Contribution

It reveals that optical spin-orbit torque governs spin switching in ferromagnets, expanding the scope of all-optical spin switching beyond ferrimagnets and establishing a new paradigm for ultrafast magnetic control.

Findings

Spin switching depends on the effective spin angular momentum exceeding a critical value.

Ferromagnets switch faster than ferrimagnets due to strong exchange coupling.

Generated magnetic field of 65 T can reduce high current in spintronics.

Abstract

Faster magnetic recording technology is indispensable to massive data storage and big data sciences. {All-optical spin switching offers a possible solution}, but at present it is limited to a handful of expensive and complex rare-earth ferrimagnets. The spin switching in more abundant ferromagnets may significantly expand the scope of all-optical spin switching. Here by studying 40,000 ferromagnetic spins, we show that it is the optical spin-orbit torque that determines the course of spin switching in both ferromagnets and ferrimagnets. Spin switching occurs only if the effective spin angular momentum of each constituent in an alloy exceeds a critical value. Because of the strong exchange coupling, the spin switches much faster in ferromagnets than weakly-coupled ferrimagnets. This establishes a paradigm for all-optical spin switching. The resultant magnetic field (65 T) is so big that it will significantly reduce high current in spintronics, thus representing the beginning of photospintronics.