Centers of Charge Nonuniformity in Absorption Spectra
of Lanthanum Manganites

N. N. Loshkareva¹, Yu. P. Sukhorukov^1, *, E. A. Neifel’d¹, V. E. Arkhipov¹,
A. V. Korolev¹, V. S. Gaviko¹, E. V. Panfilova¹, V. P. Dyakina¹,
Ya. M. Mukovski², and D. A. Shulyatev²

¹Institute of Metal Physics, Ural Division, Russian Academy of Sciences, Yekaterinburg, 620219 Russia

²Moscow State Institute of Steels and Alloys, Moscow, 117936 Russia

*e-mail: suhorukov@imp.uran.ru

Received August 4, 1999

Abstract—In order to study the microscopic nature of the phase separation in lanthanum manganites, experi-
mental investigations were made of the optical, electrical, and magnetic properties of La_1–MnO₃ and
La _0.9Sr_0.1MnO₃ lanthanum manganite single crystals. The infrared absorption spectra revealed two bands at
0.14 eV and 0.35 eV whose intensity was sensitive to the magnetic order. The different temperature dependence
of the electrical resistivity (semiconducting) and the transmission (metallic) below the Curie ferromagnetic
temperature indicates that an insulator–metal transition takes place in various regions of the insulating matrix,
i.e., phase separation occurs. Characteristic features of the properties and the nature of the phase separation in
these compounds can be explained using a model of polar (hole [Mn]_JT and electron [Mn]_JT) pseudo-
Jahn–Teller clusters which form centers of charge nonuniformity in the crystal. © 2000 MAIK “Nauka/Inter-
periodica”.

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