High pressure high temperature (HPHT) synthesis and magnetism of Cr-12s2 copper oxides with fluorite-structured layers between CuO2 planes

The three first members of the Cr-12s2 (s = 1,2,3) homologous series, i.e. CrSr2YCu2O8 (Cr-1212), CrSr2(Y1.5Ce0.5)Cu2O10 (Cr-1222) and CrSr2(Y1Ce2)Cu2O12(Cr-1232) are synthesized by high pressure high temperature (HPHT) 6 GPa and 1550 degrees C process. Though the Cr-1212 and Cr-1232 could not be formed in single phase with full Cr, the Cr- 1222 is achieved in pure phase with space group I4/mmm. These compounds belong to the multi-layered copper oxides series that differ from each other only in terms of the (Ce,Y)-[O-2-(Ce,Y)](s-1) layer blocks between two identical CuO2 planes with s = 1, 2 and 3. At 5 K, the magnetization M(H) experiments showed some ferromagnetic like hysteresis loops though the characteristic M-r and H-c were not seen clearly. None of the studied compounds exhibited superconductivity down to 5 K. (C) 2007 Published by Elsevier B.V.