Probe Mössbauer Diagnostics of Charge Ordering in Manganites CaCu.sub.xMn.sub.7-xO.sub.12

• Published in: Journal of experimental and theoretical physics 2019-12, Vol.129 (6), p.1017
• Main Authors: Glazkova, I. S, Rusakov, V. S, Sobolev, A. V, Matsnev, M. E, Gapochka, A. M, Gubaidulina, T. V, Presniakov, I. A
• Format: Article
• Language: English
• ISSN: 1063-7761; 1090-6509
• DOI: 10.1134/S1063776119110104

We present the results of our .sup.57Fe probe Mössbauer study in manganites CaCu.sub.xMn.sub.6.96-x.sup.57Fe.sub.0.04O.sub.12 (0 [less than or equal to] x [less than or equal to] 1). We have established that for compositions 0 [less than or equal to] x [less than or equal to] 0.15 near the structural R [Formula omitted] â Im [Formula omitted] transition (at T [almost equal to] T.sub.CO), an increase in the temperature leads to a decrease in the content of the rhombohedral phase (R [Formula omitted]) against a background of the "nucleation" and gradual increase in the fraction of the cubic phase (Im [Formula omitted]), in which all octahedral positions of manganese are equivalent due to the electron exchange Mn.sup.3+ â Mn.sup.4+. The increase in the electron exchange frequency is assumed to be related to a weakening of the electron-lattice interaction of Jahn-Teller Mn.sup.3+ cations as x [right arrow] 0.4. An increase in the copper content leads to a sharp decrease in the phase transition temperature T.sub.CO. A single component corresponding to the cubic phase (Im [Formula omitted]) is present in the spectrum starting from x [greater than or equal to] 0.4. Based on our Mössbauer data, we have constructed a T-x phase diagram.