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Sb − 5 s lone pair dynamics and collinear magnetic ordering in Ba 2 FeSb Se 5

2021; American Physical Society; Volume: 103; Issue: 5 Linguagem: Inglês

10.1103/physrevb.103.054115

2469-9977

Stefan Maier, Michael W. Gaultois, Nami Matsubara, T. Wesley Surta, F. Damay, S. Hébert, V. Hardy, David Berthebaud, Franck Gascoin,

Rare-earth and actinide compounds

Neutron diffraction and X-ray pair distribution function (XPDF) experiments were performed in order to investigate the magnetic and local crystal structures of Ba2FeSbSe5 and to compare them to the average (i.e. long-range) structural model, previously obtained by single crystal X-ray diffraction. Changes in the local crystal structure (i.e. in the second coordination sphere) are observed upon cooling from 295 K to 95 K resulting in deviations from the average (i.e. long-range) crystal structure. This work demonstrates, that these observations cannot be explained by local or long-range magnetoelastic effects involving Fe-Fe correlations. Instead, we found, that the observed differences between local and average crystal structure can be explained by Sb-5s lone pair dynamics. We also find, that below the N\'eel temperature (TN = 58 K), the two distinct magnetic Fe3+ sites order collinearly, such that a combination of antiparallel and parallel spin arrangements along the b-axis results. The nearest-neighbor arrangement (J1 = 6 {\AA}) is fully antiferromagnetic, while next-nearest-neighbor interactions are ferromagnetic in nature.