Sequence of phase transformations and inhomogeneous magnetic state in nanosized Sr2FeMoO6 – δ

Resumo

We have studied the effect of synthesis conditions on the phase composition, grain size and morphology, degree of superstructural ordering, and magnetic properties of the Sr₂FeMoO_6–δ double perovskite. The results demonstrate that its magnetic state, dependent on the nonuniformity of grain morphology and the degree of superstructural ordering of the iron and molybdenum cations, correlates with the initial solution pH. Analysis of the sequence of phase transformations during strontium ferromolybdate crystallization in the citrate gel process from a pH 4 starting solution allowed us to propose combined conditions that ensure the preparation of single-phase Sr₂FeMoO_6–δ powder with an average grain size in the range 50–120 nm and the highest degree of superstructural ordering of the iron and molybdenum cations: P = 88%.