Magnetoacoustic Resonance in Lithium Ferrite

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Abstract
The parametric coupling of magnetostatic and elastic modes (magnetoacoustic resonance) has been observed in a single‐crystal lithium ferrite sphere. Observation of this effect was made possible by the development of highly ordered stoichiometric lithium ferrite which has the narrowest ferromagnetic resonance linewidth of the spinel ferrimagnets [ΔH(300°K)=1.7 Oe, ΔH(134°K)=0.9 Oe at 5.4 G/sec]. The Q of the oblate‐prolate elastic mode for this sphere was found to be 175 000 at 300°K. An estimate of one of the two magnetoelastic coupling constants resulted in a value B1=65×106 erg cm−3. This estimate was made by comparing the magnetoacoustic threshold for a sphere of this material with the threshold for a sphere of yttrium iron garnet (YIG), for which the coupling constants are known. A figure of merit for magnetoelastic materials is presented on the basis of which it appears that lithium ferrite may be superior to YIG in some transducer applications.