Energy gaps in the spin-wave spectrum of rare-earth orthoferrites in a magnetic field

Temperature and field dependences of energy gaps in the spin-wave spectra at the boundaries of the orientational translation have been studied for thulium and ytterbium orthoferrites. It is shown that in transitions induced by a magnetic field, the gaps in the soft-mode spectra of iron as well as the rare earth are independent of temperature (field). A comparison of the results of high-frequency experiments on various ferrites leads to the conclusion that the contribution of longitudinal oscillations of magnetization at temperatures T < 100 K to the energy gaps in TmFeO3 and YbFeO3 is small and depends mainly on the magnetoelastic and dipole interactions, as well as on the dynamic coupling between iron and rare-earth subsystems.

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