Single-crystal growth and the dependence on hole concentration and magnetic field of the magnetic ground state in the edge-sharing CuO2 chain system Ca2+xY2-xCu5O10 -: art. no. 104413

We have succeeded in growing large-size single crystals of Ca2+xY2-xCu5O10 with 0 <= x <= 1.67 and measured the magnetic susceptibility, specific heat, and magnetization curve, in order to study the magnetic ground state in the edge-sharing CuO2 chain as a function of hole concentration and magnetic field. In the range 0 <= x <= 1.3, it has been found that an antiferromagnetically ordered phase with the magnetic easy axis along the b axis is stabilized and that a spin-flop transition occurs by the application of magnetic fields parallel to the b axis. The antiferromagnetic transition temperature decreases with increasing x and disappears around x=1.4. Alternatively, a spin-glass phase appears around x=1.5. At x=1.67 where the hole concentration is similar to 1/3 per Cu, it appears that a spin-gap state is formed owing to the formation of spin-singlet pairs. No sign of the coexistence of an antiferromagnetically ordered state and a spin-gap state as seen in Ca1-xCuO2 has been found in Ca2+xY2-xCu5O10.