Ferron-like states in YBa2Cu3O6+x

Localized hole states induced by an O- ion in the O1 position of the oxygen -deficient YBa2Cu3O6+x crystal are considered. The system is described by t he Hubbard model with the use of the spin-wave approximation. For the param eters of YBa2Cu3O6+x, the ground one-hole state is of the ferron type with a region of ferromagnetically ordered Cu spins around a hole in the Cu-O pl ane. The formation of the ferron state is ensured by the interaction of spi ns of the O- ion and copper ions of the plane. (C) 1999 Elsevier Science B. V. All rights reserved.