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) 6GPa and 1550°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)-[O2-(Ce,Y)]s−1 layer blocks between two identical CuO2 planes with s=1, 2 and 3. At 5K, the magnetization M(H) experiments showed some ferromagnetic like hysteresis loops though the characteristic Mr and Hc were not seen clearly. None of the studied compounds exhibited superconductivity down to 5K.