Micromagnetic simulation of THz signals in antiferromagnetic FeRh by sub-picosecond thermal pulses

Abstract

The generation of electrical field signals in the terahertz frequency (THz) range has gained increasing attention in recent years. The use of antiferromagnets (AFM) has been proposed as a possible alternative to generate high frequency signals using spin transfer torque (STT) induced damping compensation. In this work, we simulated a potential mechanism for laser-induced THz signals in the AFM phase of FeRh/Pt bilayer films using micromagnetic model. The FeRh film is modeled as two Fe-sublattices coupled via intra-lattice exchange field, and subjected to a sub-picosecond thermal pulse. A partial canting between the magnetizations of two Fe-sublattices, is observed within the first picosecond after the excitation. This short lived state relaxes abruptly into the initial AFM phase, injecting a spin current into the Pt layer via spin pumping, which will eventually be converted into charge current oscillating at THz frequency.