Berlin 2018 – scientific programme

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MA: Fachverband Magnetismus

MA 46: Magnonics II

MA 46.8: Talk

Thursday, March 15, 2018, 17:00–17:15, H 0110

Efficient excitation of perpendicular standing spin waves in nanometer-thick yttrium iron garnet films — •Huajun Qin, Sampo J. Hämäläinen, and Sebastiaan van Dijken — NanoSpin, Department of Applied Physics, Aalto University School of Science, P.O.Box15100, FI-00076Aalto, Finland

Spin waves in ferrimagnetic yttrium iron garnet (YIG) films are promising for low-power wave-like computing and magnon-based spintronics. The excitation frequency of spin waves in YIG is rather low because of its small saturation magnetization. For high-frequency magnonic devices, spin waves at higher frequencies are required. Here we demonstrate the efficient excitation of high-frequency exchange-dominated perpendicular standing spin waves (PSSWs) in nanometer-thick YIG films with a thin CoFeB capping layer. Using global microwave excitation fields, we measure intense PSSWs up to 10th order. We also observe strong hybridization between the PSSW modes in YIG and the FMR mode of CoFeB, causing characteristic anti-crossing behavior in the spin-wave spectra. We explain the excitation of PSSWs by a dynamic exchange torque at the YIG/CoFeB interface. The highly localized torque originates from exchange coupling between two forced magnetization oscillations of different amplitude in the YIG and CoFeB layers. As a consequence, spin waves are launched into both layers and a PSSW forms when the wave vector matches a confinement condition. No PSSWs are excited when the exchange coupling between YIG and CoFeB is suppressed by a nonmagnetic insertion layer.