INDIRECT RKKY-TYPE INTERACTION BY DIRECT OXYGEN HOPPING

The three-band Emery model, describing the holes in the CuO2 planes of the high-temperature superconducting oxides, is considered. The model includes the direct oxygen-oxygen hopping integral t(pp). The exact B ogolyubov transformation is used to exclude one oxygen band and obtain a two-dimensional Anderson model. Afterward, the effective Hamiltonia n is obtained by eliminating the second oxygen band with the use of tw o approximate canonical transformations. The effective Hamiltonian des cribes the spins residing on the copper sites and interacting through an indirect interaction J(SX)(R), where R is the distance between two copper ions. J(SX)(R) depends on the doping rate delta and is a decayi ng function of R. Numerical results for J(SX)(R) are given for differe nt doping rates delta for the case of parabolic bands. The obtained in teraction J(SX)(R), when added to the original antiferromagnetic inter action (present in oxides at delta = 0), might lead to a frustration o f the long-range antiferromagnetic ordering upon doping.