Structure and magnetic properties of the high-T-c related phase Cm2CuO4

Neutron-diffraction, x-ray absorption, and magnetic susceptibility measurem ents have been used to characterize the structural and magnetic properties in a 42-mg powder sample of Cm2CuO4. This curium compound crystallizes in t he tetragonal I4/mmm space group, and is isostructural with the R2CuO4 (R = Pr-Gd) series that become superconducting upon electron doping. The lattic e parameters, Cm-O distance, x-ray-absorption edges, and magnetic susceptib ility data indicate that the Cm is trivalent. The Cm spins order antiferrom agnetically below 25 K, although the magnetic and chemical unit cells are i dentical. The spins, which order ferromagnetically within the a-b plane, ar e antiferromagnetically coupled along the c axis, that is, adjacent planes are coupled antiparallel along c. These results are discussed in terms of t he absence of superconductivity in the Th-doped analog. [S0163-1829(99)0522 9-7].