THE LAYERED MANGANOCUPRATE EU3BA2MN2CU2O12 - AN INTERGROWTH BETWEEN THE 123 AND 0201 STRUCTURES

A manganocuprate Eu3Ba2Mn2Cu2O12 with a ''0234'' layered structure has been synthesized far the first time. This new phase crystallizes in the space group I4/mmm (a = 3.8826(1) Angstrom, c = 35.266(1) Angstrom). Its study by HREM and powder XRD shows that its structure consists of an intergrowth of single rock-salt layers with quadruple oxygen deficient perovskite layers. This structure can also be described as an intergrowth of K2NiF4-type layers, Eu2MnO4, with oxidized ''123'' layers EuBa2Cu2MnO8. The semiconducting properties and paramagnetic behaviour of this phase at temperatures above 130 K suggest a mixed valence of manganese according to the formula (Eu3Ba2MnMn)-Ba-III-Mn-(IIICu2O12)-Cu-IV-O-II. An original feature of this compound deals with the existence of two magnetic orderings at 100 and 15 K respectively. (C) 1995 Academic Press, Inc.