Curve fitting complex Moessbauer spectra; application to HoBa2(Cu0.95Fe0.05)3O7.02

A method for determining the best fit of a complex Moessbauer spectrum is presented and applied to the room temperature 57Fe Moessbauer spectrum of HoBa2(Cu0.95Fe0.05)3O7.02. The method generates many ''good fits'' as do previous methods. The ''best fit'', which is the goal of curve fitting, is selected from the class of good fits by means of a statistical test using the ''F'' function. The best fit for this compound represents 7 doublets. This is significantly larger than the previously reported number (3 or 4) of subspectra associated with REBa2(Cu1-xFex)3Oy compounds. Assuming no mixed valence, this implies 7 Fe sites. This result is also significantly larger than the previously reported number of Fe sites (1-4) in the REBa2(Cu1-xFex)3Oy compounds. For 6 of the 7 doublets, the isomer shift, quadrupole splitting and line width are strongly correlated. The valence state corresponding to these 6 doublets is high spin +4. The seventh doublet is high spin +3. The sum of Moessbauer site multiplicities is related to the number of accidental degeneracies by a sum rule. ((orig.))