Ultrafast switching of antiferromagnetic order by field-derivative torque

TL;DR

This paper demonstrates that field-derivative torque from THz pulses can deterministically switch antiferromagnetic order efficiently, with circular polarization reducing the required field and increasing switching area.

Contribution

It introduces and analyzes the use of field-derivative torque for ultrafast, deterministic antiferromagnetic switching, including effects of pulse polarization and material damping.

Findings

Field-derivative torque enables efficient antiferromagnetic switching.

Circularly polarized THz pulses halve the required magnetic field.

Switching area increases by 55% with field-derivative torque consideration.

Abstract

Control of magnetic order in antiferromagnets is a central challenge in the development of next-generation spintronic devices. Here, we propose and analyze magnetization switching driven by the field-derivative torque, a torque that originates from the time-derivative of an applied THz pulse acting on the staggered order parameter. Using atomistic spin simulations, we show that the field-derivative torque couples efficiently to the N\'eel vector, enabling deterministic switching without net spin accumulation. Further, we show that using the circularly polarised THz pulse, the FDT-induced magnetization switching reduces the required THz magnetic field by two-fold. To this end, we compute the switching and non-switching areas as a function of THz pulse width, THz magnetic field, and damping of the antiferromagnetic material. We find that the switching and non-switching areas are completely deterministic in antiferromagnets. Moreover, the switching area increases by about 55% when the FDT is considered.