Study of the ground state properties of the perovskites R(Y, Pr)BaCuT(Fe, Co)O5+y within the Hubbard model

The phase diagram and the ground state properties of the R(Y, Pr)BaCuT(Fe, Co)O5+y perovskites, where y is the concentration of the extra oxygen, have been studied using the Hubbard model. We consider two chains of magnetic i ons and allow electron hopping between sites on different chains, modeling in this way the effect of the extra oxygen atoms in the system. By doping t he system with oxygen, narrow regions of competing magnetic structures appe ar in the phase diagram and the magnetic ordering is rapidly destroyed with increasing oxygen concentration y. This is in agreement with the experimen tal results which show that magnetic ordering exists only for low extra oxy gen concentration y (y <0.08). The magnetic properties of the system are on ly locally affected by the oxygen impurities clustering. (C) 2001 American Institute of Physics.