Mossbauer spectra of Stoner-Wohlfarth particles in rf fields in a modifiedrelaxation model

A theory of Mossbauer absorption spectra in the presence of external rf fie lds is developed for Stoner-Wohlfarth particles in an extended relaxation m odel with a more realistic description of the relaxation process. Calculati ng in this model, we track the transformation of the Mossbauer spectra as a function of relaxation processes for the transitional region and frequenci es and amplitudes of the rf field where the well-resolved hyperfine structu re transitions into an isolated central peak with satellites. In this trans itional region new types of resonance effects are found which have no analo gy with previously known resonance phenomena. (C) 1999 American Institute o f Physics. [S1063- 7761(99)01709-6].