Figure 3

Experimental magnetisation dependence of the conversion area and the conversion efficiency’s maximum. The frequency f is shown versus the difference between the saturation magnetisations \(\Delta {M}_{{\rm{S}}}={M}_{{\rm{S}},1}-{M}_{{\rm{S}},2}\) at antenna 1 and 2 for the S₂₁ (a) and S₃₁ (b) parameters, respectively. The spin-wave transmission is colour coded (red: strong transmission, blue: no transmission). White squares (triangles) are the experimentally determined FMR frequencies using the reflection parameters S₁₁ (S₂₂) at antenna 1 (antenna 2). The width of the conversion area increases with decreasing saturation magnetisation (a) and the FMR frequency at antenna 2 shifts to lower frequencies. On the other hand, spin waves with a frequency larger than this FMR frequency cannot travel through the magnetisation landscape to reach antenna 3 (b). (c) The normalised efficiency of the mode conversion (black line) of BVMSWs to MSSWs is shown versus the frequency f. Here, the saturation magnetisation difference \({\rm{\Delta }}{M}_{{\rm{S}}}\) is about 16 kA⁄m. The position of the maximum is determined via fitting the experimental data with an empirical bi-Gaussian function (grey dotted line). (d) The frequency of the numerical conversion efficiency peak (red squares) is plotted versus \({\rm{\Delta }}{M}_{{\rm{S}}}\). Black circles indicate the theoretically expected position of the crossing points of the BVMSW (at antenna 1) and MSSW (at antenna 2) dispersion relations for the corresponding saturation magnetisations. The error bars result from the peak fitting error of the experimental data and the error in the external magnetic field (\({\mu }_{0}{\rm{\Delta }}{H}_{{\rm{ext}}}=\pm \,1\,{\rm{mT}}\)), respectively.