Interactive magnetic coupling between spin precession and split-ring resonator in the terahertz frequency

Terahertz metamaterial technique enables a sophisticated electromagnetic excitation of materials. Here, we demonstrate resonant excitation of spin precession motion of canted antiferromagnet ErFeO₃ using the magnetic near-field produced by split ring resonator (SRR). When the resonance frequency of spin precession was near the magnetic resonance mode of SRR, we observed substantial increase of precession amplitude. The time evolution of spin motion can be successfully reproduced by a model that takes into account an interactive coupling between spin- and SRR-resonance mediated by magnetic near-field. Results indicate that bidirectional coupling between spin and SRR is essential in understanding the system.