ZhETF, Vol. 120,
p. 470 (August 2001)
(English translation - JETP,
Vol. 93, No. 2,
available online at www.springer.com
PHASE SEPARATION IN SYSTEMS WITH CHARGE ORDERING
Kagan M.Yu., Kugel K.I., Khomskii D.I.
Received: December 25, 2000
PACS: 71.45.Lr, 75.10.-b, 75.30.Mb, 75.30.Kz
A simple model of charge ordering is considered. It is explicitly shown that at any deviation from half-filling (n
eq 1/2), the system is unstable with respect to the phase separation into the charge-ordered regions with n = 1/2 and metallic regions with a smaller electron or hole density. A possible structure of this phase-separated state (metallic droplets in a charge-ordered matrix) is discussed. The model is extended to account for the strong Hund-rule onsite coupling and the weaker intersite antiferromagnetic exchange. The analysis of this extended model allows us to determine the magnetic structure of the phase-separated state and to reveal the characteristic features of the manganites and other substances with charge ordering.