Transition from dimerization to antiferromagnetic order in quasi-one-dimensional Ca_0.83CuO₂

Abstract

Magnetic susceptibility and torque anisotropy were measured on the novel quasione-dimensional cuprate Ca0.83CuO2-δ. Substantial hole doping 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 CuO2 chains. Another interesting result 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 orientation determined.