Control of spin wave emission in ferrimagnet
Magnetization dynamics has attracted great deal of interest in recent years. In particular, the propagation characteristics of spin waves have been extensively studied because of their importance as the basis of magnonics, which aims to use packets of spin waves instead of electric currents as the information transmitter. Recently, a novel method of magnetization control has been reported. The method employs the inverse Faraday effect, where a circularly polarized light pulse nonthermally generates an effective magnetic field. The inverse Faraday effect has been described as impulsive stimulated Raman scattering. Thus, ultrafast magnetic switching is expected via the inverse Faraday effect. So far, there has been limited discussion on local spin oscillations. Non-local spin dynamics, i.e. propagating spin waves, excited by this impulsive excitation method has not been observed. By using this method, two-dimensional propagation can be observed in a non-contact manner, and broadband excitation can be realized, unlike resonant excitation with a microwave field. Here we study the two-dimensional propagation of a spin wave packet excited via the inverse Faraday effect in Bi-doped rare-earth iron garnet. Propagation in two directions, parallel and perpendicular to the magnetic field, was investigated by an all-optical pump-probe experiment. Backward volume magnetostatic waves were detected in both directions. The frequency of BVMSWs depends on propagation direction. The experimental results agreed well with the dispersion relation of backward volume magnetostatic waves.
Figure: Setup for time- and space-resolved spin wave emission
- T. Satoh, Y. Terui, R. Moriya, B. A. Ivanov, K. Ando, E. Saitoh, T. Shimura, and K. Kuroda
Directional control of spin wave emission by spatially shaped light
Nature Photon. 6, 662-666 (2012)
(See also Nature Photon. 6, 643-645 (2012) and Nature Photon. 6, 706 (2012))