Superparamagnetic relaxation Mössbauer spectra by phonon–magnon interaction using the multilevel method

A theory for superparamagnetic relaxation based on phonon-modulated exchange interaction is developed. A one-phonon direct-two-magnon inelastic scattering process is considered and it is assumed that this leads to a spin transition |S z>→|S z±1> of the total spin S. Corresponding transition probabilities and from these Mossbauer patterns are calculated. The influence of sample temperature, particle size and external magnetic field is demonstrated.