EVOLUTION WITH TIME OF THE MAGNETIC AND SPECTROSCOPIC PROPERTIES OF THE BACUO2- STUDY OF BA1-XSRXCUO2+DELTA SOLID-SOLUTIONS(DELTA PHASE )

A study of the evolution of the magnetic and spectroscopic properties of BaCuO2+x, obtained by thermal decomposition of BaCu(edta).nH(2)O (e dta = ethylenediaminetetraacetate), has been performed. The ferromagne tic behaviour of this compound is maintained with time, but a decrease in the effective magnetic number has been observed, probably due to t he changes in the oxidation states of copper ions belonging to the dis ordered part of the structure. An axial signal was observed in EPR, wh ich becomes rhombic with time. Solid solutions Ba-1. xSrxCuO2+delta ha ve been prepared by thermal treatment of metallo-organic complexes. A diminution in the magnitude of the ferromagnetic exchange interaction appears as strontium is substituted by barium. The thermal treatment o f the altered samples gives rise to their original behaviour.