Mössbauer study of ytterbium ethylsulphate

The hf parameters and the relaxation rate of Yb 3+ in YbES are deduced from the 170 Yb Mossbauer spectra between 1·3 and 30 K. The shielding factors R ≅ 0·24 and σ 2 ≅ 0·61 are derived from the experiments. The thermal variation of the relaxation rate observed between 8 and 25 K shows an additional exponential term to the previously observed Orbach and Raman processes, which is attributed to an optical mode of phonons.