Calculation of Mössbauer spectra of superparamagnets based on a spin–phonon interaction like model

Abstract Mossbauer spectra with superparamagnetic relaxation under the presence of an external magnetic field are calculated using diagonal hyperfine interaction and a multilevel model. The magnetization is described by a large spin S and spin–phonon interaction spin–transition probabilities are calculated from a Debye model using S =3222, Δ S 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 reduced S =322 or 32 demonstrate almost identical patterns when the temperature is adequately reduced.