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首页> 外文期刊>Physical review >Charge disproportionation in RNiO_3 (R = Tm, Yb) perovskites observed in situ by neutron diffraction and ~(57)Fe probe Moessbauer spectroscopy
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Charge disproportionation in RNiO_3 (R = Tm, Yb) perovskites observed in situ by neutron diffraction and ~(57)Fe probe Moessbauer spectroscopy

机译：通过中子衍射和〜（57）Fe探针Moessbauer光谱原位观察到RNiO_3（R = Tm，Yb）钙钛矿中的电荷歧化

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摘要

An in-situ investigation from high-resolution neutron powder diffraction data on the structural evolution of TmNiO_3 and YbNiO_3 perovskites across the metal-insulator transition, with T_(MI)= 596 K and 598 K, respectively, allowed the charge disproportionation effect that these perovskites experience upon electronic localization below TMI tobe followed.In the insulating (semiconducting) regime, the perovskites are monoclinic, space group P2_1, containing two inequivalent Ni1~((3+σ))+ and Ni2~((3-σ)+) cations; above T_(MI), the samples become orthorhombic, space group Pbnm, with a single site for Ni~(3+).The ~(57)Fe Moessbauer spectra of iron-doped (at 1.5%) aeNi03 (R = Tm, Yb) samples recorded below T_(MI) exhibit for Fe1 and Fe2 (replacing Ni1 and Ni2 sites) hyperfine parameters corresponding to large (NilO_6) and small (Ni2O_6) octahedra.The remarkable difference between the quadrupole splittings (Δ_1≈0.3 mm/s and Δ_2 ≈ 0.07 mm/s) of Fe1 and Fe2 sites in RNi_(0.985)Fe_(0.015)O_3 is analyzed.We calculate the lattice contribution to the electric field gradient (EFG) at ~(57)Fe ions, and estimate, by using the experimental Δ1 and Δ2 values, the contributions of the 3d, 3p, and 2p electrons (overlap distortion and covalence effects).Above T_(MI), a unique state for iron atoms is observed, upon metallization of the sample.
机译：根据高分辨率中子粉末衍射数据对TmNiO_3和YbNiO_3钙钛矿在金属-绝缘体跃迁上的结构演化进行了原位研究，分别具有T_（MI）= 596 K和598 K，这使得电荷歧化效应钙钛矿经历了在TMI以下电子定位的经历。在绝缘（半导体）状态下，钙钛矿为单斜晶系，空间群P2_1 / n，包含两个不等价的Ni1〜（（3 +σ））+和Ni2〜（（3-σ ）+）阳离子；在T_（MI）以上，样品变成正交晶体，空间群为Pbnm，单个位点为Ni〜（3+）。掺铁（1.5％）aeNi03的〜（57）Fe Moessbauer光谱（R = Tm，记录在T_（MI）以下的Yb）样品表现出Fe1和Fe2（取代Ni1和Ni2位置）超精细参数，分别对应于大（NilO_6）和小（Ni2O_6）八面体。四极劈裂之间的显着差异（Δ_1≈0.3mm / s分析了RNi_（0.985）Fe_（0.015）O_3中Fe1和Fe2位的Δ_2≈0.07 mm / s），计算了〜（57）Fe离子对电场梯度（EFG）的晶格贡献，并估算，通过使用实验Δ1和Δ2值，3d，3p和2p电子的贡献（重叠畸变和共价效应）。在T_（MI）之上，在样品金属化后观察到铁原子的唯一状态。

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  • 来源
    《Physical review》 |2013年第18期|184111.1-184111.12|共12页
  • 作者

    J.A.Alonso; M.J.Martinez-Lope; I.A.Presniakov; A.V.Sobolev; V.S.Rusakov; A.M.Gapochka; G.Demazeau; M.T.Fernandez-Diaz;

  • 作者单位

    Instituto de Ciencia de Materielles de Madrid,C.S.I.C.,Cantoblanco, E-28049 Madrid, Spain;

    Instituto de Ciencia de Materielles de Madrid,C.S.I.C.,Cantoblanco, E-28049 Madrid, Spain;

    Lomonosov Moscow State University, Leninskle Gory, Moscow 119992, Russia;

    Lomonosov Moscow State University, Leninskle Gory, Moscow 119992, Russia;

    Lomonosov Moscow State University, Leninskle Gory, Moscow 119992, Russia;

    Lomonosov Moscow State University, Leninskle Gory, Moscow 119992, Russia;

    ICMCB-CNRS, University Bordeaux 1 'Sciences and Technologies' Site de TENSCBP,87 Avenue du Dr.A.Schweitzer, 33608 PESSAC Cedex, France;

    Institut Laue-Langevin,B.P.156, F-38042 Grenoble Cedex 9, France;

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  • 关键词

    metal-insulator transitions and other electronic transitions; charge-density-wave systems;

    机译：金属-绝缘体过渡和其他电子过渡;电荷密度波系统;

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