Figure 3
From: Engineering optical mode ferromagnetic resonance in FeCoB films with ultrathin Ru insertion
The Ru spacer thickness dependence of FMR frequency, (a) scattering coefficient S21 at zero magnetic field, and (b) the FMR frequency of the strongest FMR peak on each sample. The absorption peak of S21 represents the FMR frequency. For the sample without Ru spacer or with thinner ones, the FMR shows acoustic mode resonance with low frequency (tRu = 0 and 2 Å). When the Ru spacer is 3–4 Å (slightly thicker than 1 ML), only optical mode resonance is observed due to the extinction of the acoustic mode resonance (tRu = 3 and 4 Å). With further increasing the Ru thickness (tRu = 8 and 11 Å), the strength of interlayer exchange coupling is weakened and both optical and acoustic mode resonances co-exist.
