Efficient spin excitation via ultrafast damping-like torques in antiferromagnets

Abstract

Damping effects form the core of many emerging concepts for high-speed spintronic applications. Important characteristics such as device switching times and magnetic domain-wall velocities depend critically on the damping rate. While the implications of spin damping for relaxation processes are intensively studied, damping effects during impulsive spin excitations are assumed to be negligible because of the shortness of the excitation process. Herein we show that, unlike in ferromagnets, ultrafast damping plays a crucial role in antiferromagnets because of their strongly elliptical spin precession. In time-resolved measurements, we find that ultrafast damping results in an immediate spin canting along the short precession axis. The interplay between antiferromagnetic exchange and magnetic anisotropy amplifies this canting by several orders of magnitude towards large-amplitude modulations of the antiferromagnetic order parameter. This leverage effect discloses a highly efficient route towards the ultrafast manipulation of magnetism in antiferromagnetic spintronics.

Canted spin order as a platform for ultrafast conversion of magnons

“…As the laser pulse duration is much shorter than the spin precession period, we may approximate the pulses to act as a Dirac delta function 27 , 43 , arriving at time t 1 and t 2 .…”

The 2022 magneto-optics roadmap

“…Finally, one can employ inverse quadratic MO effect to manipulate Néel vector of AFM by pump-probe technique [60] (see section 10), maybe even to induce selective magnetic precession of different elements. Also, one can envisage pump-probe system used to measure QMOKE spectroscopy in AFM.…”

“…To be able to measure QMOKE spectra in AFM materials, one needs to establish control of Néel vector, either statically or dynamically (precession). Control of Néel vector is clearly interesting also in other branches of physics, such as AFM spintronics or AFM spin dynamics [60]. Wellestablished inverse quadratic MOKE can contribute to achieve such a control.…”

A perspective on nonlinearities in coherent magnetization dynamics

“…This process was recently found to be capable of inducing spin precessions with amplitudes comparable to the field-torque contribution despite a ( 1. 41 Although optically induced spin deflection angles of up to 1 have been observed experimentally, 43 questions remain on how to enhance such impulsive spin excitations to enable not only the observation of magnetization dynamical nonlinearities, but also magnetic switching. A key bottleneck of impulsive excitation mechanisms arises from the fundamentally limited spectral overlap between the exciting optomagnetic field and the spin precession frequency [see Fig.…”