Estimation of the degree of crystallographic ordering of magnetoactive ions in Sr<sub>2</sub>FeMoO<sub>6</sub><sub>-</sub><sub>δ</sub> by means of the intensity of the X-ray peak (101)
Strontium ferromolybdate (Sr<sub>2</sub>FeMoO<sub>6</sub><sub>-</sub><sub>δ</sub>, SFMO) having a double Perovskite structure shows good promise as a basic material for spintronics. However SFMO has not yet found wide application due to the low reproducibility of its magnetic properties which partially originates from their strong dependence on the ordering degree of Fe and Mo ions in the <i>B</i>′ and <i>B</i>″ sublattices of double perovskite A<sub>2</sub><i>B</i>′<i>B</i>″O<sub>6</sub>. We have considered a rapid method of determining strontium ferromolybdate disorder degree. Sublattice population with Fe and Mo ions has been estimated for stoichiometric and nonstoichiometric Sr<sub>2</sub>FeMoO<sub>6</sub><sub>-</sub><sub>δ</sub> with a 5% Fe and Mo excess, respectively. We have calculated the intensity ratio between the superstructural ordering (101) peak and the most intense (112 + 200) peak. The calculated curves have been fitted to the analytical expression for similar cases known from literature. The calculation results obtained using this method are in agreement with the results of experimental data processing using the Rietveld method accurate to within ±25 %. Thus this method can be used instead of the Rietveld method if the exposure time set in an X-ray diffraction experiment is insufficient. We have discussed the dependence of the <i>I</i>(101)/<i>I</i>(112 + 200) peak intensity ratio on various factors including diffraction peak instrumental broadening, peak twinning due to grain size reduction, thin film lattice parameter variation due to substrate lattice mismatch and lattice parameter variation due to oxygen vacancies. The method is useful as it allows evaluating the superlattice ordering degree in Sr<sub>2</sub>FeMoO<sub>6</sub><sub>-</sub><sub>δ</sub> without large time consumption for X-ray diffraction pattern recording and processing with the Rietveld method which may be essential when dealing with large amounts of experimental data.