Diffusion model of superparamagnetic relaxation

To study the Mössbauer spectra of single-domain particles the full description of superparamagnetic relaxation as a diffusion process is applied. It is shown that the fluctuations of magnetic moment around the easy axes (collective magnetic excitations) play a crucial role in the relaxation behaviour of the spectra. For instance the slow fluctuations in low-dissipative magnetic particles should be followed by very broad and asymmetrical shape of hyperfine structure in Mössbauer spectra that has much in common with frequently observed anomalies.