Structural phase transition in CuFe2O4 spinel

• Published in: Crystallography reports Vol. 58; no. 5; pp. 710 - 717
• Main Authors: Balagurov, A. M., Bobrikov, I. A., Maschenko, M. S., Sangaa, D., Simkin, V. G.
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01.09.2013
• Subjects: Crystallography and Scattering Methods; Physical Properties of Crystals; Physics; Physics and Astronomy; Interplanar Distance; Crystallography Report; Structural Phase Transition; Tetragonal Phase; Inverse Spinel
• ISSN: 1063-7745; 1562-689X
• DOI: 10.1134/S1063774513040044

A structural transition with a reduction in symmetry of the high temperature cubic phase (sp. gr. Fd 3 m ) to the tetragonal phase (sp. gr. I 4 1 / amd ) and the appearance of a ferrimagnetic structure occur in CuFe 2 O 4 copper ferrite at T ≈ 440°C. It is established by an experiment on a high-resolution neutron diffractometer that the temperature at which long-range magnetic order occurs is higher than that of tetragonal phase formation. When cooling CuFe 2 O 4 spinel from 500°C, the equilibrium coexistence of both phases is observed in a fairly wide temperature range (∼40°C). The composition studied is a completely inverse spinel in the cubic phase, and in the tetragonal phase the inversion parameter does not exceed few percent ( x = 0.06 ± 0.04). At the same time, the phase formed upon cooling has a classical value of tetragonal distortion (γ ≈ 1.06). The character of temperature changes in the structural parameters during the transition from cubic to tetragonal phase indicates that this transition is based on the Jahn-Teller distortion of (Cu,Fe)O 6 octahedra rather than the mutual migration of copper and iron atoms.