Sr3CuIrO6, a spin-chain compound with random ferromagnetic-antiferromagnetic interactions

Ac and dc magnetization and heat-capacity (C) measurements performed on the pseudo-one-dimensional compound Sr3CuIrO6 reveal a competition between ant iferromagnetic (AF) and ferromagnetic (F) exchange couplings, as evidenced by frequency dependence of ac susceptibility and by the absence of a C anom aly at the magnetic transition. The value of the saturation moment (about 0 .35 mu (B)/formula unit) is much smaller than expected for ferromagnetism f rom the two S = 1/2 ions (Cu and Ir). Thus, this compound is not a ferromag net in zero magnetic field, in contrast to earlier beliefs. Of particular i mportance is the finding that the value of the magnetic ordering temperatur e is :sample dependent, sensitive to synthetic conditions resulting from de viations in oxygen/Cu content. We propose that this compound serves as a un ique model system to test theories on random AF-F interaction in a chain sy stem, considering that this competition can be tuned without any chemical s ubstitution. (C) 2001 Elsevier Science Ltd. All fights reserved.