Evaluation of the low temperature Mössbauer spectra of YBa2(Cu0.9Fe0.1)3O6.9 by means of a field distribution model
57Fe Mössbauer spectra of YBa2(Cu0.9Fe0.1)3O6.9 measured at low temperatures show spontaneous magnetic ordering combined with broad resonance lines. It is shown that these spectra can be well understood assuming an asymmetric distribution of the absolute values of the magnetic field at the nucleus. For the fitting procedure, we used the full Hamiltonian for combined electric and magnetic static hyperfine interaction. The number of free parameters for the fits was restricted as much as possible. For the iron sites A and B (Cu(1) sites), the ordering temperature is 26.5 K, for the iron site C (Cu(2) site), it is 31 K. The mean saturation hyperfine magnetic field is different for the different iron sites (26 T for the A site, 20 T for the B site and 43.5 T for the C site). Using these fit results and our results on thin films, we can give a consistent interpretation of the Mössbauer spectra of YBa2(Cu1-xFex)3O7-δ.