Crystallographic and magnetic properties of (Cu_(1-x)V _x)V_2S_4 (x≈0.3) single crystals with the layered defect NiAs structure synthesized under high pressure

摘要

We report on the reproducible growth of (Cu_(1-x)V _x)V_2S_4 single crystals of sizable dimensions (～0.3 mm) and homogeneous composition (x≈0.3) by means of high-pressure synthesis. The refinement of single crystal X-ray diffraction data indicates that the crystal structure is of the monoclinic defect NiAs-type, which consists of a stacking of VS_2 layers with CdI_2-type structure and chains of edge-sharing (Cu_(1-x)V_x)S_6 octahedra. Layers and chains form a network of face-sharing octahedra with no CuV intra-chain ordering. A combined X-ray photoelectron spectroscopy and bond valence sum analysis indicates that the valence of the V and Cu ions are 3 and 1, respectively. Magnetic susceptibility measurements unveil the coexistence of a large Pauli-like and of a small Curie-like paramagnetic contributions, with no evidence of any long range order down to 2 K. This result suggests a picture of predominantly itinerant 3d V electrons with significant electronelectron correlations.