Mossbauer spectroscopy, superparamagnetism and ferrofluids

Some fundamentals of Mossbauer spectroscopy and of fluctuating magnetic hyp erfine interactions are reviewed. An expression for calculation of spin-pho non interaction transition probabilities on the ground of a Debye model is given. Basic ideas of superparamagnetism and classical results for low-temp erature relaxation rates are presented. A theory of superparamagnetism base d on spin-phonon interaction is introduced. It is shown how to calculate fr om this Mossbauer spectra taking all spin-levels into account. Experimental spectra of ferrofluids are compared with simulated spectra and found in go od accordance.