Regensburg 2019 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 8: Magnonics

MA 8.11: Vortrag

Montag, 1. April 2019, 17:45–18:00, H52

Frequency multiplication in ferromagnetic layers detected by diamond nitrogen-vacancy centers — •Chris Körner, Niklas Liebing, Rouven Dreyer, and Georg Woltersdorf — Martin Luther University Halle-Wittenberg

We demonstrate that inhomogenous magnetic properties can lead to frequency multiplication effects. Close to ferromagnetic resonance, this effect locally generates high harmonics of the magnetic driving field. In the experiment, we detect multiple harmonics as well as parametric excitations in thin ferromagnetic layers via scanning time-resolved Kerr microscopy (MOKE) [1]. The spatial frequencies of the response of the magnetic system increases at higher harmonics up to the diffraction-limited resolution of the microscope. Nitrogen-vacancy defect centers (NV-centers) in diamond can be used as local probe of magnetic fields. Here we employ a double-resonant optical detection of magnetic resonance (ODMR) in NV-centers in the vicinity of the ferromagnetic layer [2]. The NV-centers represent a highly localized probe for the dynamic magnetic fields produced by the precessing magnetization in the adjacent ferromagnet. By this means, it is possible to locally detect rf-magnetic fields with spatial frequencies beyond the optical diffraction limit of MOKE. We use this method to detect up to the 20th harmonic of the magnetic excitation frequency in Permalloy at low bias fields and frequencies (as low as 100 MHz) as well as parametric excitations at large driving amplitudes.

[1] R. Dreyer et al. arXiv:1803.04943 [cond-mat.mes-hall] (2018)

[2] C. S. Wolfe et al. ArXiv 1512.05418v2 (2016)