Studies of FMR Linewidth in Thick YIG Films Grown by Liquid Phase Epitaxy

Epitaxial films of YIG, in the thickness range 2 μm to 100 μm, have been grown on GGG substrates by liquid phase epitaxy. Ferromagnetic resonance linewidths have been measured using the bandstop filter and cavity resonance techniques. Linewidth measurements of the principal resonance in thick YIG films are complicated by the excitation of magnetostatic modes almost degenerate with the principal resonance. This problem is reduced in the bandstop filter by the matching of electromagnetic fields to the principal magnetostatic mode due to strong coupling. Increased coupling results in frequency translation of the principal resonance into a region of low magnetostatic mode density. Under these circumstances, linewidths of as low as 0.06 Oe have been measured. Planar, high Q, high rejection microwave bandstop filters have been developed which have characteristics significantly better than dielectric resonator filters.