Magnetic properties of the S=1/2 quasi-one-dimensional antiferromagnet CaCu2O3 -: art. no. 144418

We report single-crystal growth and magnetic susceptibility and neutron diffraction studies of the S = 1/2 quasi-one-dimensional antiferromagnet CaCu2O3. The structure of this material is similar to that of the prototype two-leg spin-ladder compound SrCu2O3. However, the Cu-O-Cu bond angle in the ladder rungs in CaCu2O3 is equal to 123 degrees, and therefore the magnetic interaction along the rung is expected to be much weaker in this material. At high temperatures, the magnetic susceptibility of CaCu2O3 can be decomposed into a contribution from one-dimensional antiferromagnetic chains or finite-size chain segments together with a weak Curie contribution. The intrachain magnetic exchange constant J(parallel to), determined from the magnetic susceptibility measurements, is 2000+/-300 K. CaCu2O3 undergoes a Neel transition at T-N = 25 K with ordering wave vector of [0.429(5), 1/2, 1/2]. The magnetic structure is incommensurate in the direction of the frustrated interchain interaction. Weak commensurate magnetic Bragg peaks with the reduced wave vector (1/2, 1/2, 1/2) are also observed below T-N. Application of a magnetic field induces a metamagnetic transition at which the incommensurability of the magnetic structure is substantially reduced. Above the transition field, the material possesses only short-range magnetic order, and no well defined temperature-driven transition is observed.