On the Clock Frequency of the Néel-Vector Mode in Antiferromagnets

The potential use of antiferromagnets in high-frequency information processing is investigated by comparing different types of of Néel-vector rotations. The modes involve a competition between interatomic exchange J and anisotropy K, with basic frequencies in the ranges of several GHz (K) and several THz (J). Pure Néel-vector rotation (the propeller mode) yields GHz frequencies, whereas the scissor mode is exclusively based on J. The textbook analysis of antiferromagnetic resonance reveals a hybridization of propeller and scissor modes with precession frequencies scaling as (J K)^1/2. In general, higher frequencies correspond to weaker signals, which is a challenge in AFM spintronics. Our focus is on multiferroic switching [1] using crystal-field interactions [2-3]. Using model calculations, we show that electrostatic crystal-field changes can lead to resonance with very large precession angles and eventually yields a propeller state that corresponds to a partial magnetization switching.