Calculation of Mossbauer spectra of superparamagnets based on a spin-phonon interaction like model

Mossbauer spectra with superparamagnetic relaxation under the presence of a n external magnetic field are calculated using diagonal hyperfine interacti on and a multilevel model. The magnetization is described by a large spin S and spin-phonon interaction spin-transition probabilities are calculated f rom a Debye model using S = 3222 DeltaS(z) = +/- 2 and realistic parameters of the constants involved. It is shown that the calculated spectra exhibit the typical shape of experimental spectra. Spectra calculated with a reduc ed S = 322 or 32 demonstrate almost identical patterns when the temperature is adequately reduced. (C) 2001 Elsevier Science BN. All rights reserved.