The cooperative Jahn–Teller effect and anti-isostructural phases in Ni1−xCoxCr2O4 solid solutions: Synchrotron X-ray diffraction study. (November 2015)

• Record Type: Journal Article
• Authors: Mikheykin, A.S.; Torgashev, V.I.; Yuzyuk, Yu.I.; Bush, A.A.; Talanov, V.M.; Cervellino, A.; Dmitriev, V.P.
• Is Part Of: Journal of physics and chemistry of solids. Volume 86(2015:Nov.)
• Page Start: 42
• Page End: 48
• Publication Date: 2015-11
• Subjects: A. Ceramics -- C. X-ray diffraction -- D. Phase transitions -- D. Crystal field -- D. Crystal structure; Solids -- Periodicals; Solides -- Périodiques; Solids; Periodicals; 530.41
• DOI: 10.1016/j.jpcs.2015.06.015
• Languages: English
• ISSNs: 0022-3697

Abstract

Abstract: A low-temperature high-resolution powder diffraction study has been carried out on a system of Ni 1 − x Co x Cr 2 O 4 solid solutions with x ≤ 0.1 down to 5 K. The tetragonal phase ( I 4 1 / amd ) with c / a < 1 was experimentally observed in Ni 0.9 Co 0.1 Cr 2 O 4 below ∼64 K. The new phase is anti-isostructural to the well-known tetragonal phase of NiCr2 O4 . A unified phenomenological model has been applied to structural phase transitions in Ni 1 − x Co x Cr 2 O 4 solid solutions. It shows that the appearing of such a phase is justified from a structural point of view. Analysis of atomic displacements confirms predictions of the symmetry-based model-free consideration. Abstract : Highlights: A low temperature XRPD study has been carried out on Ni 1 − x Co x Cr 2 O 4 solid solutions. The new tetragonal phase with c / a < 1 was observed in Ni 0.9 Co 0.1 Cr 2 O 4 below 64 K. Analysis of atomic displacements confirms predictions of symmetry-based consideration. Oxygen octahedra distortion leads to formation of tetragonal phase with c / a < 1 .