Detection of focused beams of surface magnetostatic waves in YIG / Pt structures

Abstract

The purpose of this work is to experimentally study, using the inverse spin Hall effect (ISHE), the detection of focused beams of magnetostatic surface waves (MSSW) in integrated YIG (3.9 µm) / Pt (4 nm) thin-film microstructures, where the focusing effect was ensured by the curvilinear shape of the exciting antenna. Make a comparison with the case of detecting MSSWs excited by a rectilinear antenna. Methods. Experiments were carried out using the delay line structures based on the YIG/Pt. The amplitude-frequency characteristics of the YIG/Pt structure and the frequency dependence of the EMF (V(f)) induced in platinum were studied. Results. It was shown that at frequencies f near the long-wavelength limit of the MSSW spectrum, the magnitude of the EMF V(f) generated by a focused MSSW can be several times higher than the values of V(f) in the case of MSSW excitation by a common (straight) antenna. In this case, in the short-wavelength part of the spectrum, on the contrary, the magnitude of the EMF generated by the focused MSSW beam turns out to be noticeably smaller. This behavior is associated with chromatic aberration of the focusing antenna for the MSSW, which manifests itself in the frequency dependence of the focal length of the antenna, which is confirmed by the results of micromagnetic modeling. It is shown that the drop in the EMF signal generated by a focused MSSW beam in the short-wavelength part of the spectrum is associated with the focus reaching the area of the YIG not covered with the Pt film. In this case, the increase in V(f) in the long-wavelength region of the MSSW spectrum is explained by an increase in the linear power density of the MSSW and the formation of caustics under the Pt film. Conclusion. Obtained results can be used for the development of highly sensitive spin wave detectors and the creation of spin logic devices.