Small‐Angle Neutron Scattering and Magnetically Heterogeneous State in Sr₂FeMoO_6–δ

Abstract

Single‐phase strontium ferromolybdate (Sr2FeMoO6–δ) samples with different degrees of the superstructural ordering of the Fe/Mo cations (P) are obtained from partially reduced SrFeO3–х, SrMoO4 precursors by the solid‐state technology. The study of the temperature dependences of the magnetization measured in the field‐cooling and zero‐field‐cooling modes indicated an inhomogeneous magnetic state of the samples. The presence of magnetic regions of different nature has also been revealed by the small‐angle neutron scattering. For the Sr2FeMoO6–δ samples with different P values and for all values of the magnetic field induction up to 1.5 T and of the scattering vector in the interval 0.1 > q > 0.002 Å−1, the analytical dependence I ∼ q–α obeys the Porod law (α ≈ 4), which corresponds to an object with a smooth and well‐marked surface and polydisperse grain size. Deviations from the Porod law in the q > 0.1 Å−1 region and a weakening of the neutron scattering in applied magnetic fields may be ascribed to magnetic inhomogeneities with diameters D < 6 nm, which are partially destroyed/oriented by magnetic fields В ≥ 1.5 T. It is established that the magnetic homogeneity of the Sr2FeMoO6–δ compound is enhanced with increasing superstructural ordering of the Fe/Mo cations.

Magnetization of Magnetically Inhomogeneous Sr2FeMoO6-δ Nanoparticles

“…For K 1 ≈ 1.7 × 10 5 J/m 3 (cf. Section 4), we find µ 0 H c ≈ 12 mT (the measuring field was µ 0 H = 10 mT) in accordance with the experimental value of µ 0 H c ≈ 12-14 mT at 4.2 K of similar samples, but pressed into pellets and long-term annealed at 1420 K in a flux of a gas mixture of 5% H 2 /Ar [18].…”

Resistivity and Tunnel Magnetoresistance in Double‐Perovskite Strontium Ferromolybdate Ceramics

“…For SFMO–SMO core‐shell structures, the coercive field at 4.2 K amounts to 2 μ 0 H c ≈ 24−28 mT. [ 84 ] With increasing temperature, the coercive field decreases. [ 85 ]…”

Magnetic, Magnetocaloric, and Electric Transport Properties of Sr2FeMoO6–δ Double Perovskites with Different Degrees of Superstructural Ordering

“…This coupling is responsible for the appearance of antiferromagnetic clusters, which were observed in small‐angle neutron scattering measurements. [ 19 ]…”

“…This coupling is responsible for the appearance of antiferromagnetic clusters, which were observed in small-angle neutron scattering measurements. [19] Another exchange mechanism that can be realized in double perovskites assumes itinerant electron spin contribution into total magnetic moment. In the framework of the model [20] incorporating this assumption, T C is proportional to density of states at the Fermi level.…”