Dielectrics

Exchange interaction in LaCoO$_3$ between cobalt ions Co$^{3+}$ in different spin states

S. I. Polukeev, V. A. Gavrichkov, S. G. Ovchinnikov

L. V. Kirensky Institute of Physics, Siberian Branch of the Russian Academy of Sciences, Krasnoyarsk, Russia

Abstract: The values and signs of the contributions to the superexchange interaction of Co$^{3+}$ ions in LaCoO$_3$ in different spin states, namely, the superexchange of a pair of ions in the intermediate (IS) state and the superexchange of a pair of ions, one of which is in the intermediate state and the other in the high-spin (HS) state, are studied. For this purpose, virtual electron-hole pairs produced in the course of superexchange (the so-called exchange loops) have been studied within the framework of a multiband generalization of the Hubbard model. It is shown that the cobalt ions in the intermediate state are ordered ferromagnetically, while a pair of ions in different HS and IS states makes an AFM contribution to the superexchange.

Keywords: superexchange interaction, magnetic structure, Hubbard model, projection operator method, exchange loop.

Received: 07.07.2022
Revised: 07.07.2022
Accepted: 10.07.2022

DOI: 10.21883/FTT.2022.12.53642.426

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