High magnetic ordering temperature in the perovskites Sr4−xLaxFe3ReO12 (x=0.0, 1.0, 2.0)

A series of perovskites Sr4−xLaxFe3ReO12 (x=0.0, 1.0, 2.0) has been prepared by wet chemistry methods. The structure analyses by powder X-ray and neutron diffraction and electron microscopy show that these compounds adopt simple perovskite structures without cation ordering over the B sites: tetragonal (I4/mcm) for x=0.0 and 1.0 and orthorhombic (Pbmn) for x=2.0. The oxidation states of the cations in the compound with x=0.0 appear to be Fe3+/4+ and Re7+ and decrease for both with La substitution as evidenced by X-ray absorption spectroscopy. All the compounds are antiferromagnetically ordered above room temperature, as demonstrated by Mössbauer spectroscopy and the magnetic structures, which were determined by powder neutron diffraction. The substitution of Sr by La strongly affects the magnetic properties with an increase of TN up to ∼750 K.

High resolution transmission electron microscopy image of Sr4−xLaxFe3ReO12 (x=2.0), showing twin domains. Fourier transforms are given of the areas indicated by the circles.Figure optionsDownload as PowerPoint slideHighlights
► Sr4−xLaxFe3ReO12 (x=0.0, 1.0, 2.0) perovskites prepared by wet chemistry.
► PXD, PND, ED, indicate no cation ordering, I4/mcm) for x=0.0, 1.0, Pbmn for x=2.
► XAS show oxidation states Fe3+/4+ and Re7+; both decrease with increasing x.
► All order antiferromagnetically above RT, with highest TN ∼750 K.