Evidence of new layered cuprates in the Hg-A-Gd-Cu-O system (A=Ba, Sr)

Syntheses, structures, electrical and magnetic properties of Hg(1-x)Gd(x)A(2)GdCu(2)O(7-delta) (A = Ba, Sr) and Hg2-xGdxBa2GdCu2O8-delta layered cuprates have been reported. These compounds crystallize in tetragonal 1212- and 2212-type structures, respectively. They are prepared under normal oxygen pressure and are semiconductors. Magnetic susceptibility measurements reveal antiferromagnetic ordering of Gd magnetic moments in both 1212 and 2212 compounds in a narrow temperature range (T-N = 2.25-2.4 K). Electron microscopy studies of the Hg-Ba-Gd-Cu-O system prepared under an oxygen pressure of a few bars evidenced intergrowths between the 1212 and 123 structures.