Dresden 2020 – scientific programme

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MA: Fachverband Magnetismus

MA 45: Magnonics I

MA 45.11: Talk

Thursday, March 19, 2020, 12:15–12:30, HSZ 401

Threshold determination of non-linear spin-wave generation at low magnetic bias field — •Rouven Dreyer, Niklas Liebing, Chris Körner, and Georg Woltersdorf — Martin Luther University Halle-Wittenberg, Institute of Physics, Von-Danckelmann-Platz 3, 06120 Halle (Saale), Germany

Recently it was shown that the prediction of the non-linear spin-wave excitation in the framework of Suhl instability processes is not adequate at low magnetic bias fields. In particular, it was shown by spatially averaged and time-resolved x-ray ferromagnetic resonance spectroscopy that in the low bias field regime non-linear spin waves are excited parametrically at 3/2 of the excitation frequency [1].

Here we demonstrate the 3/2 ω non-linear spin-wave (NLSW) generation in Ni₈₀Fe₂₀ microstructures using a novel variant of scanning magneto-optical microscopy which we term super-Nyquist sampling microscopy (SNS-MOKE) [2]. This technique allows for phase-resolved imaging of the sample at multiple arbitrary frequencies. In this way we detect parametrically excited NLSWs at 3/2 of the excitation frequency in space and time directly. For this type of non-linearities we determine the threshold rf-field for different sample geometries and investigate the phase stability of the NLSW generation as a function of rf-field and bias field. The corresponding wave vectors obtained from the 2D-FFT of the observed spatially resolved spin-wave pattern at 3/2 ω above the threshold rf-field are in agreement with the predictions from Bauer et al. [1]. [1] H. G. Bauer et al., Nat. Commun. 6:8274 (2015) [2] R. Dreyer et al., arXiv:1803.04943 (2018)