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Ferromagnetic resonance detection in magnetic single objects via a novel microresonator and microantenna approach
Cansever, H.ORC; Lenz, K.ORC; Narkowicz, R.; Kowalska, E.ORC; Faßbender, J.ORC; Deac, A. M.; Lindner, J.
Ferromagnetic resonance has been commonly used as a spectroscopic technique investigating the fundamental properties of ferromagnetic materials, such as magnetization, g-factor, magnetic anisotropy and damping (relaxation) parameters [1-4].Conventionally, an FMR spectrometer is operating at a fixed microwave frequency to detect the microwave absorption of the magnetic object by sweeping an external magnetic field through the resonance. The sensitivity of this weak absorption process is typically enhanced by using a microwave bridge setup. However, for a reliable quantification of key magnetic parameters like the g-factor or spin relaxation times, the measurements should be performed within a broad range of frequencies. This is achieved by broadband FMR spectrometers which employ vector network analyzers (VNA) that detect the microwave transmission or reflection parameters of the sample [5-6]. However, neither conventional cavities nor broadband FMR spectrometers are able to detect signals of micro/nano size samples due to the tiny sample volume. To achieve optimal sensitivity for small objects, planar microresonators were introduced for electron paramagnetic resonance (EPR) experiments [7]. Microresonators have been used to investigate magnetization dynamics of magnetic object to understand uniform and spin wave modes [8], as well as the spin-Seebeck effect in magnetic tunnel junctions [9.] The microresonator approach allows producing rf magnetic fields homogeneously concentrated inside a metallic loop, thereby increasing the filling factor of the resonator. Here, we explain the novel microesonator approach in detail and introduce moreover a microantenna approach which allows to perform experiments in the range of 8-18 GHz employing a co-planar layout. We investigate magnetization dynamics within Permalloy (Ni80Fe20) wires by using both, microresonator and microantenna approach.

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Keywords: ferromagnetic resonance, microresonator, microantenna
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Publ.-Id: 29814