The influence of cation ordering and oxygen nonstoichiometry on magnetic properties of Sr₂FeMoO_6-x, around Curie temperature

Sr2FeMoO6-x polycrystalline samples with different oxygen content (6 - x) and various degrees of super-structural ordering of Fe/Mo cations (P) were obtained by the solid-phase method from the SrFeO2.52 and SrMoO4 precursors. From the investigation on the influence of oxygen non-stoichiometry and the P parameter on the magnetic properties of Sr2FeMoO6-x, it was found that with an increase in P and a decrease in the (6 - x) value from 5.99 to 5.94, an increase in the magnetization values is observed in the temperature range 77-600 K. For all the Sr2FeMoO6-x samples there is a tendency that P value rises with increasing x, where, accordingly, the volume fraction of regions in which there are no anti-structural defects increases as well. This is also indicated by Mossbauer spectroscopy data, confirming an increase in the area of the S1 sextet corresponding to Fe ions in highly ordered regions and a decrease in the area of the S2 sextet associated with disordered regions. Using the temperature scanning method, the temperatures of the onset and completion of the transition from the paramagnetic to the ferrimagnetic state and, correspondingly, the blurring width of the transition have been estimated. It turned out that with decreasing P, the blurring of the transition increases, which is associated with an increase in the concentration of anti-structural defects.