Observation of Magneto-Elastic Effects in Terbium Metal by Ferromagnetic Resonance atλ=2.5−3mm

Abstract

Magneto-elastic effects recently included in theoretical studies of spin-wave spectra of heavy rare-earth metals have suggested that millimeter ferromagnetic-resonance (FMR) results in terbium metal should be reinvestigated. We present data here from a new, detailed study of FMR in single-crystal terbium metal. The data extend over a wider temperature range (13-240 K) than was previously reported, and at frequencies of 98 to 121 GHz. Angular studies were also made. The high-frequency FMR data are qualitatively the same as those reported earlier, and agree qualitatively with theoretical calculations from the model which assumes that elastic strains are "frozen" at the equilibrium (i.e., no spin-wave) configuration. Quantitative fitting of the theory to the data requires values of the anisotropy and magneto-elastic constants that are in reasonable agreement with the results of other studies. Our values are $P_{2}S=-18\mathrm{}$ K/atom and $D^{\gamma }=1.7\mathrm{}$ K/atom. The present paper provides a solution to the puzzling discrepancy which has existed for several years between our earlier high-frequency FMR results and Cooper's theoretical predictions.