Inertia-driven spin switching in antiferromagnets

Abstract

Magnetic switching is typically accomplished by using a driving field that stays on until the magnetization is rotated to its final position. An experiment demonstrates that, in antiferromagnets, inertial effects can be harnessed, such that only a short ‘kick’ is required to transfer sufficient momentum to the spin system for it to reorient. It is generally accepted that the fastest way to reorient magnetization is through precessional motion in an external magnetic field1,2,3,4,5,6,7. In ferromagnets, the application of a magnetic field instantaneously sets spins in motion and, in contrast to the inertial motion of massive bodies, the magnetization can climb over a potential barrier only during the action of a magnetic-field pulse. Here we demonstrate a fundamentally different scenario of spin switching in antiferromagnets, where the exchange interaction between the spins leads to an inertial behaviour. Although the spin orientation hardly changes during the action of an optically generated strong magnetic-field pulse of 100 fs duration, this pulse transfers sufficient momentum to the spin system to overcome the potential barrier and reorient into a new metastable state, long after the action of the stimulus. Such an inertia-based mechanism of spin switching should offer new opportunities for ultrafast recording and processing of magnetically stored information.