Structural and magnetic properties on F-doped LiVO_2 with two-dimensional triangular lattice

摘要

The layered oxide LiVO_2 recently has received more attention due to its interesting structural and magnetic behaviors involving the two-dimensional magnetic frustration in these systems. We synthesized a series of F-doped LiVO_2 samples, and reported the F-doping effect on the structure and transition temperature T,. The samples LiVO_(2-x)F_x (x=0, 0.1, 0.2 and 0.3) were characterized by X-ray diffraction, scanning electron microscope (SEM), differential scanning calorimetry (DSC), magnetic susceptibility and specific heat measurement. The structural analysis shows that with increasing x, the ratio of lattice parameter c/a increasing, i.e. in the a-b plane the lattice is compressed while in the c-axis direction the lattice expands. The DSC measurements show that a first-order phase transition happens at around 500 K, and the thermal hysteresis around phase transition temperature T, increases with increasing x. Substitution of O with F ions results in a change of two dimensional characteristics and the distortion of the VO_6, block in structure, which significantly influence the magnetic ordering transition temperature T_t.