FMR linewidth measurements in bismuth-substituted YIG

The ferromagnetic resonance linewidth ΔH has been measured on films of Y3−xBixFe5O12 with x values of 0, 0.41, and 1.03 and for temperatures from 5 to 550 K. The measurements were made at 9.3 GHz, with the applied field perpendicular to the film plane. The films are about 1 μm thick. We find that for T near the Néel temperature, ΔH is about 1.5 Oe for x=1.03 as opposed to 3.5 Oe for pure YIG. The minimum value of ΔH for the pure LPE YIG is about 1/3 Oe at room temperature. The minimum linewidth for x=1.03 is 0.4 Oe at 160 K while for x=0.41 the narrowest linewidth observed was 0.2 Oe at 2.5 K. For this sample the linewidth was a monotonically increasing function of temperature while for x=0 and 1.03, maxima occurred at about 50 K.