Transition from Dimerization to Antiferromagnetic Order in Quasi-One-Dimensional Ca(0.83)CuO(2)

Magnetic susceptibility and torque anisotropy were measured on the novel quasi-one-dimensional cuprate Ca(0.83)CuO(2-delta). Substantial hole doping of between 0.27 and 0.36 holes/Cu can be achieved by
changing the oxygen content. This strongly influences dimerization, which originates from a modulated exchange coupling in the CuO(2) chains. Another interesting result for this one-dimensional system is the unexpected
transition at T=12.2(1) K into an antiferromagnetic ordered state in spite of the high doping. By torque analysis
the existence of an easy axis in this ordered state was clearly demonstrated and its precise orientation determined.