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On the origin of neutron magnetic scattering in anti-site disordered Sr2FeMoO6 double perovskites

D. Sanchez·J. A. Alonso·M. Garcia-Hernandez·M. J. Martinez-Lope·J. L. Martinez·A. Mellergard
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Abstract

Anti-site disordering in Sr2FeMoO6 double perovskites (containing Mo atoms at Fe positions, and viceversa) has recently been shown to have a dramatic influence in their magnetic and magnetotransport properties. In the present study, two polycrystalline Sr2FeMoO6 samples showing different degrees of anti-site 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 (NPD) techniques in the 15-500K temperature range. Our main finding is that the 'disordered' sample exhibits a strong magnetic scattering (noticeable even at 500K), comparable to that displayed by the 'ordered' one below TC= 415 K. For the 'disordered' sample, the magnetic scattering exhibited on low angle Bragg positions, is not to be ascribed to a (non-existent) 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.

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D. Sanchez, J. A. Alonso, M. Garcia-Hernandez, M. J. Martinez-Lope, J. L. Martinez, A. Mellergard. 2001-11-28. On the origin of neutron magnetic scattering in anti-site disordered Sr2FeMoO6 double perovskites. https://doi.org/10.1103/physrevb.65.104426

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