On the importance of anisotropic exchange coupling on to the structure of spin-polarized clusters in layered cuprates

The low energy spectrum of spin-polarized clusters in layered cuprates is examined. Two types of clusters confining the motion of oxygen holes are discussed. The ground state of the pentanuclear copper cluster has a total spin S = 2, whereas the one of the tetranuclear copper cluster is characterised by S= 3/2. Anisotropic exchange coupling splits the magnetic ground state into a sequence of state, which in a natural way provide e.g. an explanation of EPR data for La₂CuO_4+δ compounds.