title: Suppression of phase transitions at low temperature by chromium substitution in vanadium spinel Fe(V1-x Cr x )2O4.
abstract: Synchrotron powder diffraction, magnetization, and specific heat measurements have been used to investigate the structural and magnetic phase transitions in the spinel-type vanadate Fe(V1-x Cr x )2O4 (0.0  ⩽  x  ⩽  1.0). We observed five different transitions in our polycrystalline samples. The canted-type ferrimagnetic phase transition accompanied by the lattice distortion was suppressed by Cr substitution (x  =  0.2). Additionally, high-resolution synchrotron powder diffraction revealed that the low-temperature orthorhombic phase appears in FeV2O4 below 30 K and disappears by subtle Cr doping. In contrast, for x  ⩾  0.7, we observed a different magnetic transition of possibly conical-type ferrimagnetic ordering that did not induce significant lattice distortion at the transition temperature. We performed structural refinements for low-temperature phases and suggest that the crystal system of Fe(V1-x Cr x )2O4 at 15K is an orthorhombic lattice for all x values. In the orthorhombic phase, a unique behaviour was observed, with the lattice constants a and b approaching each other as Cr doping increased. This behaviour can be explained by the change of orbitally ordered states of the Fe(2+) ions.
authors.affiliation: Research & Utilization Division, Japan Synchrotron Radiation Research Institute (JASRI/SPring-8), 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Kawaguchi
authors.forename: H
authors.initials: H
authors.lastname: Ishibashi
authors.forename: K
authors.initials: K
authors.lastname: Nagami
authors.forename: Y
authors.initials: Y
authors.lastname: Kubota