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

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.

12 page2, 6 figures. Accepted to Europhysics Letters (2016). Extended version with the supplementary information. Contribution from Indiana State University,Europhysics Letters (2016)

References in corpus (4)

• Spin Transfer Torques
• All-optical control of ferromagnetic thin films and nanostructures
• Magnetic switching dynamics in a ferrimagnetic two sub-lattice model including ultrafast exchange scattering
• Manipulating Femtosecond Spin--Orbit Torques with Laser Pulse Sequences to Control Magnetic Memory States and Ringing

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• Is perpendicular magnetic anisotropy essential to all-optical ultrafast spin reversal in ferromagnets?
• First-principles insights into all-optical spin switching in the half-metallic Heusler ferrimagnet Mn${}_2$RuGa
• Heisenberg representation of nonthermal ultrafast laser excitation of magnetic precessions
• Gateway to all-optical spin switching in Heusler ferrimagnets: Pancharatnam-Berry tensor and magnetic moment ratio
• Demagnetizing fields in all-optical switching