"CaCu2O3" - A nonstoichiometric compound: Structural disorder and magneticproperties

In the compounds MgCu2O3 and CaCu2O3 the Cu and O atoms are connected topol ogically in the same way as in the fascinating spin-ladder compound SrCu2O3 . In contrast to the latter, the Cu-O-Cu bonding angle corresponding to the "rungs" is significantly less than 180 degrees in MgCu2O3 and CaCu2O3. As a consequence, the magnetic susceptibility is quite different compared with that of SrCu2O3. Single-phase samples of CaCu2O3 revealed a deficiency of Ca, a balancing excess in Cu, and an oxygen deficiency corresponding to Ca1 -xCu2+xO3-delta. The excess Cu atoms, which are located near the Ca sites, are in the 3d(10) state. The deficiency of oxygen causes a Curie term in th e magnetic susceptibility due to the interruption of Cu-O-Cu bonds. From th e overall behavior of the susceptibility an antiferromagnetic ordering at a Mel temperature of about 27 K is concluded. (C) 2001 Elsevier Science Ltd. All rights reserved.