Supertransferred hyperfine interactions in layer LaSrGa0.995Cu0.005O4

The EPR allowing a direct observation of supertransferred hyperfine fields on the nuclei of the next-nearest cations to copper ion in the structure of LaSrGa0.995Cu0.005O4 isomorphous to the superconducting cuprates prove the far delocalisation of the spin density. The theoretical analysis of the value and mechanisms of this process by the method of configurational interaction leads to a good agreement with the experiment. It is shown that the cascade processes involving simultaneous electron transfers from the oxygen to the copper atom and from the neighbouring cation to the same oxygen, in the fragment considered bring a substantial contribution into polarisation of 3s-shell of gallium ion. A comparison of the supertransferred hyperfine fields and g-tensor values in the studied, diluted LaSrGa0.995Cu0.005O4 crystal and in the La2CuO4 cuprate confirms the validity of the local centre approach in the analysis of cuprate properties. © 2002 Elsevier Science B.V. All rights reserved