Elektricheskaya polyarizatsiya v dvoynom manganite BiMn7O12: messbauerovskoe issledovanie na zondovykh yadrakh 57Fe

Abstract

The electrical hyperfine interactions of the probe 57Fe nuclides localized in the structure of the quadruple manganite BiMn7O12 are studied by Mössbauer spectroscopy. The measurements are carried out in the temperature range 101 K T 447 K, where this manganite has a nonzero spontaneous electric polarization (Ps); moreover, this range includes the temperature (T* ≈ 240 K) of the P1 ↔ Im structural phase transition. The parameters of the hyperfine interactions of the partial spectra of the 57Fe nuclei are comprehensively analyzed, and their crystal-chemical correspondence to certain positions of Jahn–Teller Mn3+ ions in the structure of manganite is performed. The “dynamic” Born charge model is used to develop an algo rithm to construct the temperature dependence of the polarization of the crystal Ps(T) using structural data of the compound and the experimental values of the quadrupole splittings Δ(T) of the Mössbauer spectra of the 57Fe probe atoms. The Ps(T) dependences obtained on both sides of point T* are analyzed in terms of the mean-field model.