High Temperature Metal−Insulator Transition Induced by Rare-Earth Doping in Perovskite CaMnO3

详细信息    查看全文

• 作者：Yang Wang ; Yu Sui ; Jinguang Cheng ; Xianjie Wang ; Zhe Lu ; Wenhui Su
• 刊名：Journal of Physical Chemistry C
• 出版年：2009
• 出版时间：July 16, 2009
• 年：2009
• 卷：113
• 期：28
• 页码：12509-12516
• 全文大小：260K
• 年卷期：v.113,no.28(July 16, 2009)
• ISSN：1932-7455

文摘

This paper reports the crystal structure and high-temperature transport properties of electron-doped perovskite manganites Ca_0.9R_0.1MnO₃ (R = La, Pr,..., Yb). All the samples crystallized into a orthorhombic distorted perovskite structure (space group Pnma). The structural distortion increases as the average A-site cation size r_A decreases; the average Mn−O−Mn bond angle θ_Mn−O−Mn monotonously decreases, while the average Mn−O bond length d_Mn−O exhibits a minimum at R = Dy. The substitution of R³⁺ for Ca²⁺ markedly enhances the electrical conductivity of parent CaMnO₃ and induces a metal−insulator transition at T_MI which varies from 325 K to 420 K with R³⁺. Among all the samples, Ca_0.9Dy_0.1MnO₃ shows the lowest resistivity and T_MI, mainly because of its shortest d_Mn−O and largest effective bandwidth W. Thermally activated conductivity is valid below T_MI, and the activation energy increases slightly with the structural distortion. All of the samples exhibit metallic-like behavior above T_MI. The measurements of magnetic susceptibility and the Seebeck coefficient indicate that the metal−insulator transition with R³⁺ doping is induced by the spin-state transition of Mn³⁺ ions, and the transition is strongly influenced by the crystal structure. Moreover, the observed T_MI can be well described as a function of the structural parameters θ_Mn−O−Mn and the A-site cation size variance σ².