Origin of neutron magnetic scattering in antisite-disordered Sr 2 FeMoO 6 double perovskites

By D. Sánchez, J. Alonso, M. García-Hernández, M. J. Martínez-Lope, J. L. Martínez, A. M. ICMM-CSIC, NFL-Studsvik. 2001

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Antisite disordering in Sr2FeMoO6 double perovskites ~containing Mo atoms at Fe positions, and vice versa! has recently been shown to have a dramatic influence in their magnetic and magnetotransport properties. In the present paper, two polycrystalline Sr 2FeMoO6 samples showing different degrees of antisite disorder ~a nominally ‘‘ordered’’ sample with ;70% of cationic ordering and a nominally ‘‘disordered’’ sample with ;18% of cationic ordering! have been examined by magnetic measurements and neutron powder diffraction techniques in the 15‐500 K temperature range. Our main finding is that the ‘‘disordered’’ sample exhibits a strong magnetic scattering ~noticeable even at 500 K!, comparable to that displayed by the ‘‘ordered’’ one below TC5415 K. For the ‘‘disordered’’ sample, the magnetic scattering exhibited on low-angle Bragg positions, is not to be ascribed to a ~nonexistent! ferrimagnetic ordering: our results suggest that it originates upon naturally occurring groups of Fe cations in which strong antiferromagnetic ~AFM! Fe-O-Fe superexchange interactions are promoted, similar to those existing in the LaFeO3 perovskite. These Fe groups are not magnetically isolated, but coupled by virtue of Fe-O-Mo AFM interactions, which maintain the long-range coherence of this AFM structure. Susceptibility measurements confirm the presence of AFM interactions below 770 K.

Subfields: Condensed Matter Physics, Electronic, Optical and Magnetic Materials

View Paper: https://www.semanticscholar.org/paper/dc0e3da8719447511dfa7c254b212030abf4fcca