Dresden 2017 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 65: Poster 2

MA 65.12: Poster

Freitag, 24. März 2017, 09:30–13:00, P2-OG1

Microwave interferometry for high sensitivity VNA-FMR measurements — •Taras Holoyad, Joschua Kurda, Sibylle Sievers, and Hans Werner Schumacher — Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig

Vector network analyzer ferromagnetic resonance (VNA-FMR) using coplanar waveguides (CPW) is widely used to analyze ferromagnetic film parameters. This is of particular interest in the area of patterned magnetic nanostructures, where, however, due to the small volume, the absorption inn FMR is low and the FMR signal is superimposed by the excitation signal, limiting the sensitivity. Here, a promissing approach is microwave interferometry [1]. In the present work, we compare two techniques to generate the reference signal to interfere with the signal of the measurement path:

(I) A reference signal is generated in a second microwave path with the same geometry as the measurement path, including an identical but empty CPW. It is, however, extended by 0.5 m of an rf coaxial cable. This path length difference leads to a frequency dependent phase difference of the two paths in regular frequency intervals. (II) The second technique uses a fully synthetic reference signal generated by a second phase coherent microwave source with adjustable attenuation.

Our experiments reveal an improvement of the sensitivity by up to 2 orders in magnitude. The feasibility of both techniques is discussed.

[1] S. Tamaru et al, Ultrahigh Sensitivity Ferromagnetic Resonance Measurement based on Microwave Interferometer, IEEE Magn. Lett., Volume 5 (2014).