| Summary: | 碩士 === 國立中山大學 === 物理學系研究所 === 105 === Vanadates oxide materials exhibit a variety of functional properties whose origin is closely related to the structural and electronic peculiarities of the compounds. Recently, in the vanadatesTM2V2O7 (TM = Cu, Co and Ni), a magnetically driven ferroelectric phenomena has been reported. The multiferroic ordering of these system closely connected with the crystal structure and their magnetic properties. The crystallographic structure for Co2V2O7 exhibits a dichromate structure with crystallizes in a monoclinic symmetry, whereas Cu2V2O7 crystallizes in two different polymorphs (I) α-structure, that is orthorhombic and noncentrosymmetric, and the (II) -phase that is monoclinic and centrosymmetric. In Co2V2O7, two Co2+O6 cations octahedral connected via edge sharing and forms the zigzag chains along c-axis and chains are separated by nonmagnetic (V2O7)4- groups that lead to frustrated one dimensional antiferromagnetic ordering. On the other hand, in α-Cu2V2O7, Cu2+O5 polyhedral form the cross-linking chain network which are separated by (V2O7)4- anion units makes system a weak ferromagnet ground state induced by Dzyaloshinskii-Moriya (DM) interaction. In these present study, we are doping the small concentration (5%) of magnetic (Co) and nonmagnetic (Zn and Ga) elements to understand the effect of doping on the structural magnetic and dielectric properties of α-Cu2V2O7. Our magnetization data clearly indicates that the Co doping significantly modifies the ground state magnetic property by invoking the frustration. However nonmagnetic elements does not show much influence on the strength of DM interaction of α-Cu2V2O7. We believe local structural modulation by chemical doping with different doping element might alters the magnetic ground state of α-Cu2V2O7.
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