Study On The Synthesis And Physical Properties Of One-dimensional Spin Chain Material Li_1-xCuVO₄(x≤0.2)

In this dissertation, two different ways to synthesize one-dimensional spin chain LiCuVO₄ are presented. In the first instance, the Citrate Sol-Gel method is employed to synthesize single crystal LiCuVO₄. From observation by the optical microscope, it has homogeneous and transparent appearance. The SEM and EDX used to characterize both micro structure and component of single crystal LiCuVO₄. EDX result reveals the atom ratio of Cu:V:O is equal to 1:1:4 which makes chear these is no impurity in it. Then, the single crystal sample is investigated by Raman scattering. Consequently, two sharp peaks appeared at Raman shift equals to 227cm^-1and 350 cm^-1 which represent very strong B1 gvibration. This type of vibration can be explained by using effect of multi-phonon scattering deduced by site shift of Li+ iron in the lattice. Besides, due to the cooperation among magnetic sub systems in the crystal, theoretical duo-peak does not appear instead of one broaden peak at the Raman shift equals to 738cm^-1.For the second part as a further step, solid phase reaction is employed to synthesize powder LiCuVO₄. Since main physics properties are induced by CuO2 which plays a role as unit cell of one-dimensional chain system. We manage to introduce holes inside the chain of Cu-O, with mean of reduce concentration of Li+. Series Li_1-xCuVO₄ samples are synthesized. XRD spectrum reveals sample is pure LiCuVO₄ while electron-hole density(x) is smaller 0.2, which means if x is larger than 0.2 impurity phase will generate. It can be concluded through the calculation that with the density of Li⁺ decreasing, the lattice parameter enlarges simultaneously. The Raman scattering spectrum presents that the sharp peak of B1g appeared in previous single crystal sample is crippled by hole doping. By characterization of valance state with high definition XPS, we find that decrease of Li⁺ will transform some Cu²⁺ to Cu³⁺. This can also be proved through the following investigation of magnetic properties of the hole doped samples. The SQUID is used to detailly understand the magnetic properties of Li_1-xCuVO₄ samples. It shows that decreases due to some magnetic Cu²⁺ transform to nonmagnetic Cu³⁺. At the mean time, it is convinced that the sample's susceptibility in the low temperature zone is contributed by both"Courier term"and some ferromagnetic interaction in the system. The ferromagnetic momentum in the hole doped system is investigated as well.