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首页> 外文期刊>Physical review >Role of intrinsic disorder in the structural phase transition of magnetoelectric EuTiO_3
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Role of intrinsic disorder in the structural phase transition of magnetoelectric EuTiO_3

机译：本征无序在磁电EuTiO_3结构相变中的作用

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摘要

Up to now, the crystallographic structure of the magnetoelectric perovskite EuTiO_3 has been considered to remain cubic down to low temperature. Here we present high-resolution synchrotron x-ray powder-diffraction data showing the existence of a structural phase transition, from cubic Pm-3m to tetragonal I4/mcm, involving TiO_6 octahedra tilting, in analogy to the case of SrTiO_3. The temperature evolution of the tilting angle and of the full width at half maximum of the (200) cubic reflection family indicate a critical temperature T_c = 235 K. This critical temperature is well below the recent anomaly reported by specific-heat measurement at T_A ～ 282 K. By performing atomic pair distribution function analysis on diffraction data, we provide evidence of a mismatch between the local (short-range) and the average crystallographic structures in this material. Below the estimated T_e, the average model symmetry is fully compatible with the local environment distortion, but the former is characterized by a reduced value of the tilting angle compared to the latter. At T = 240 K, data show the presence of local octahedra tilting identical to the low-temperature one, while the average crystallographic structure remains cubic. On this basis, we propose that intrinsic lattice disorder is of fundamental importance in the understanding of EuTiO_3 properties.
机译：迄今为止，磁电钙钛矿EuTiO_3的晶体结构一直被认为在低温下仍保持立方。在这里，我们提供高分辨率的同步加速器X射线粉末衍射数据，类似于SrTiO_3的情况，该数据显示了从立方Pm-3m到四方I4 / mcm的结构相变的存在，涉及TiO_6八面体倾斜。倾斜角和（200）立方反射族的半峰全宽的温度演变表明临界温度T_c = 235K。该临界温度远低于T_A〜的比热测量报告的最近异常。 282K。通过对衍射数据进行原子对分布函数分析，我们提供了该材料中局部（短程）和平均晶体学结构不匹配的证据。在估计的T_e以下，平均模型对称性与局部环境变形完全兼容，但是前者的特征是与后者相比，其倾斜角值减小。在T = 240 K时，数据表明存在与低温相同的局部八面体倾斜，而平均晶体结构仍保持立方。在此基础上，我们提出内在晶格无序对理解EuTiO_3性质至关重要。

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  • 来源
    《Physical review》 |2012年第18期|p.184107.1-184107.8|共8页
  • 作者

    Mattia Allieta; Marco Scavini; Leszek J. Spalek; Valerio Scagnoli; Helen C. Walker; Christos Panagopoulos; Siddharth S. Saxena; Takuro Katsufuji; Claudio Mazzoli;

  • 作者单位

    Dipartimento di Chimica Fisica ed Elettrochimica, Universita degli Studi di Milano, Via Golgi 19, 20133 Milano, Italy;

    Dipartimento di Chimica Fisica ed Elettrochimica, Universita degli Studi di Milano, Via Golgi 19, 20133 Milano, Italy;

    Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE, United Kingdom,Department of Physics, University of Crete and FORTH, GR-71003 Heraklion, Greece;

    Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland,European Synchrotron Radiation Facility, 6 rue Jules Horowitz, Boite Postale 220, 38043 Grenoble Cedex 9, France;

    European Synchrotron Radiation Facility, 6 rue Jules Horowitz, Boite Postale 220, 38043 Grenoble Cedex 9, France;

    Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE, United Kingdom,Department of Physics, University of Crete and FORTH, GR-71003 Heraklion, Greece,Division of Physics and Applied Physics, Nanyang Technological University, Singapore;

    Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE, United Kingdom;

    Department of Physics, Waseda University, Tokyo 169-8555, Japan;

    Politecnico di Milano, p.zza L. Da Vinci 32, 1-20133 Milano, Italy European Synchrotron Radiation Facility, 6 rue Jules Horowitz, Boite Postale 220, 38043 Grenoble Cedex 9, France;

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  • 关键词

    magnetomechanical and magnetoelectric effects, magnetostriction; ferroelectricity and antiferroelectricity;

    机译：磁机械和磁电效应;磁致伸缩;铁电和反铁电;

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