Unidirectional control of optically induced spin waves (Vol. 48, No. 4)

For future information technologies, the field of magnonics is rapidly emerging. Spin waves ̶collective modes of spin precessions ̶ are promising information carriers in magnonics, as Joule heating is negligible and propagation damping is low. Spatial control of the spin wave is indispensable for future application such as spin-wave switching, spin-wave-assisted recording, and sensing of small magnetic fields. In this article, unidirectional control of optically induced spin waves in a rare-earth iron garnet crystal is demonstrated. We observed the interference of two spin-wave packets with different initial phases generated by circularly polarized light pulses. This interference results in unidirectional propagation if the spin-wave sources are spaced apart at 1/4 of the wavelength of the spin waves and the initial phase difference is set to π/2. The propagating direction of the spin wave is switched by the polarization helicity of the light pulses. Moreover, in a numerical simulation, applying more than two spin-wave sources with a suitable polarization and spot shape, arbitrary manipulation of the spin wave by the phased array method was replicated. This achievement opens up a field of magnetic materials science and explores an alternative sensing technique using magnetic fields.

I. Yoshimine, Y. Y. Tanaka, T. Shimura and T. Satoh, Unidirectional control of optically induced spin waves, EPL 117, 67001 (2017)
[Abstract]