Jahn-Teller Ordering Dynamics in the Paraelectric BiMn.sub.7O.sub.12 Phase: .sup.57Fe Probe Mössbauer Diagnostics

• Published in: Journal of experimental and theoretical physics Vol. 137; no. 3; pp. 404 - 412
• Main Authors: Sobolev, A. V, Nitsenko, V. I, Belik, A. A, Glazkova, I. S, Kondratyeva, M. S, Presniakov, I. A
• Format: Journal Article
• Language: English
• Published: Springer 01-09-2023
• Subjects: Electric fields
• ISSN: 1063-7761
• DOI: 10.1134/S1063776123090145

The electrical hyperfine interactions of the .sup.57Fe probe nuclei stabilized in the structure of the BiMn.sub.7O.sub.12 manganite are studied by Mössbauer spectroscopy. Mössbauer spectra are measured in the para-electric temperature range, which includes the structural phase transitions I2/m â Im [Formula omitted] (T.sub.1 [almost equal to] 600 K) and Im â I2/m (T.sub.2 [almost equal to] 450 K). The calculation of the parameters of the electric field gradient tensor with allowance for the dipole contributions of Bi.sup.3+ cations in the range of the first phase transition allowed us to confirm a random orientation of the dipole moments p.sub.Bi in the cubic phase of the manganite (Im [Formula omitted]). Based on an analysis of the Mössbauer spectra recorded at T.sub.2 < T < T.sub.1, we considered various scenarios for the manifestation of the dynamic Jahn-Teller effect, which leads to the "melting" of the orbital order in the manganese sublattice, in terms of a two-level relaxation model.