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[89] Ruderman-Kittel-Kasuya-Yosida interaction versus superexchange in a plane in the limit


The indirect exchange interaction between localized Cu spins via mobile O holes is derived from the three-band Anderson lattice model for copper oxides for infinite Hubbard repulsion at Cu sites. By means of two nested canonical transformations, Ruderman-Kittel-Kasuya-Yosida (RKKY) and superexchange interactions are found in the fourth order of the Cu-O hybridization amplitude, where both O bands are consequently taken into account. For nearest neighbours the RKKY coupling and the superexchange integral , which increase with the direct O-O transfer, differ in sign and undergo a sign change upon doping. overcompensates .

Journal of Physics: Condensed Matter / Volume 10 / Number 3
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Winfried Kolley
PD Dr. rer. nat. habil. Winfried Kolley