Magnetic Resonance in Single-Crystal Dysprosium at 100 GHz

The microwave absorption of a single crystal of dysprosium at 100 GHz was studied as a function of temperature and magnetic field applied in the magnetically hard $〈10\overline{1}0〉$ direction. A peak in the absorption is attributed to ferromagnetic resonance, and the temperature dependence of the field value at which the resonance occurs is compared with previous theories. The results provide what is believed to be the first unambiguous evidence that magnetoelastic effects are important in the spin-wave spectrum of dysprosium at high microwave frequencies. The best fit between experiment and theory requires a value of the $c$-axis anisotropy constant less than half that derived from static measurements: i.e., $-2\mathrm{}{P}_{2}S=21.\mathrm{}6$ K/atom, rather than 50.4 K/atom. The value of the magnetoelastic coupling constant that gave the best fit was $D^{\gamma }$ =1.4 K/atom, comparable to the static value of 1.1 K/atom.