Magnetic moment configuration: One of decisive factors to enhance the optical mode resonance in interlayer exchange coupled trilayers

Abstract

The optical mode (OM) ferromagnetic resonance (FMR) pushes the frequency of soft magnetic films from 10 to 20 GHz, showing a great engineering application prospect in monolithic microwave integrated circuits. However, the determinants of OM frequency and intensity remain unclear. In this study, three magnetic moment configurations (MMCs) with uniaxial anisotropy, quasi-isotropy, and isotropy were established respectively to explore the effect of MMCs on the OM FMR performances in FeCoB/Ru/FeCoB trilayers with the same average compositions and geometry. No detectable FMR signal was observed in the isotropic sample, while an ultrahigh OM frequency frO of 15.91 GHz with parentheses-shaped angle distribution of FMR intensity was present in the uniaxial anisotropic sample. In contrast, a high frO of 13.29 GHz also exists in the quasi-isotropic sample, but its angle distribution of FMR intensity likes a circle, indicating an omnidirectional frO distribution. This sample is very beneficial for the OM engineering application due to its omnidirectional frO distribution, which breaks through the limitation of magnetic anisotropy to the shape design of magnetic microwave components. It can be concluded that, although three trilayers have the same compositions and geometry, completely different OM resonance performances result from the difference of MMCs, i.e. the MMC is a decisive factor for OM resonance. This study provides the design basis and optimization method for magnetic material fabrication and their device design.