Large angle amplitude "spin strain waves"

DIPC Seminars

Lucia Aballe, ALBA Synchrotron Light Facility
Donostia International Physics Center
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Large angle amplitude "spin strain waves" Surface Acoustic Waves (SAW) are propagating strain waves that can be generated through oscillating electric fields at the surface of piezoelectric materials. They can couple to a magnetic material in heterostructures comprising both a piezoelectric and a magnetic material. The mutual coupling of SAW and magnetic material through strain and magnetoelasticity has been mostly investigated by averaging or indirect methods [1-4] which could not resolve the dynamics of the interaction. Using stroboscopic XPEEM with X-ray circular magnetic dichroism (XMCD) contrast, we have previously investigated the dynamic response of magnetic flux closure states in patterned nanostructures upon excitation with a SAW which is synchronized to the 500 MHz repetition rate of the ALBA synchrotron [5]. In this talk I present our studies on “strain spin waves” over macroscopic areas in continuous nickel thin films, deposited onto piezoelectric substrates (LiNbO3) capable to produce directional SAW. By exciting with different SAW frequencies (125 MHz - 500 MHz), we have directly imaged collective magnetic excitations with large angular modulation of the magnetization and with the spatial periodicity of the corresponding SAW. These coupled modes propagate over mm long distances thanks to the SAW and provide interesting perspectives for the development of magnonic devices. References [1] S. Davis et al., Appl. Phys. Lett. 97, 232507 (2010). [2] M. Weiler et al., Phys. Rev. Lett. 106, 117601 (2011). [3] M. Weiler et al., Phys. Rev. Lett. 108, 176601 (2012). [4] L. Thevenard et al., Phys. Rev. B 90, 094401 (2014). [5] M. Foerster et al. Nat. Comm. 8, 407 (2017). Host: Celia Rogero