Mössbauer relaxation spectra of the spherical superparamagnetic particles with zero energy of anisotropy

Superoperator equations of Fokker-Planck type, describing the common dynamics of the hyperfine field and the nuclear spin are derived under the conditions of diffusional motion of the magnetic moment of the particles. The solution of this equation in the case of particles with zero energy of magnetic anisotropy is considered. Mössbauer spectra of⁵⁷Fe nuclei are calculated over a large range of the diffusion coefficient.