Mossbauer spectroscopy of CsCoCl3 doped with 57Fe and Mg

In this work Mossbauer spectra of CsCo1-x-y57FexMgyCl3 (where x ∼ 1% and y=0.07, 0.3, 0.7, 2.6%) in powdered form have been taken for a range of temperatures from 250 K down to 5.5 K. The spectra of these compounds taken below 21 K could be analysed in the same way as the spectra of CsCo0.09Fe0.01Cl3 where the fits to the spectra are consistent with the magnetic phases of pure CsCoCl3. CsCoCl3 is a one-dimensional Ising-like antiferromagnet and moving domain walls or 'solitons' have been observed in the one-dimensionally ordered Co2+ chains from ∼ 75 K down to 9 K. At 9 K full three-dimensional order is formed. However, experiments on Mg-doped CsCoCl3 indicate that the Mg suppresses this transition so that it may be possible for solitons to be present below 9 K. No unequivocal evidence to indicate the presence of solitons below 9 K in Mg-doped CsCoCl3 could be found in the Mossbauer spectra. It was found that the addition of the Mg lowers the temperature of the transition to the partially disordered phase, TN1, from 21.1±0.3 K (no Mg) to 19.6±0.3 K (2.6 at.% Mg). The spectra of CsCoCl3 doped with 2.6 at.% Mg showed differences that resulted in soliton relaxation rates which were approximately a factor of two higher than the rates determined for the other compounds. In all compounds the soliton relaxation rates determined above 9 K were found to be between one and two orders of magnitude below the theoretical prediction for a non-interacting soliton gas and it is suggested that this model is not appropriate for CsCoCl3. (author)