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首页> 外文期刊>Physical review >High-pressure synthesis and characterization of the effective pseudospin S = 1/2 XY pyrochlores R_2Pt_2O_7 (R = Er, Yb)
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High-pressure synthesis and characterization of the effective pseudospin S = 1/2 XY pyrochlores R_2Pt_2O_7 (R = Er, Yb)

机译：高压合成和表征有效的假自旋S = 1/2 XY烧绿石R_2Pt_2O_7（R = Er，Yb）

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摘要

We report on the high-pressure syntheses and detailed characterizations of two effective pseudospin S=1/2 XY pyrochlores Er_2Pt_2O_7 and Yb_2Pt_2O_7 via x-rayeutron powder diffraction, dc and ac magnetic susceptibility, and specific-heat measurements down to 70 mK. We found that both compounds undergo long-range magnetic transitions at T_(N,C) ≈ 0.3 K, which are ascribed to an antiferromagnetic- and ferromagnetic-type order for Er_2Pt_2O_7 and Yb_2Pt_2O_7, respectively, based on the field dependence of their transition temperatures as well as the systematic comparisons with other similar pyrochlores R_2B_2O_7 (R = Er, Yb; B = Sn, Ti, Ge). The observed T_N of Er_2Pt_2O_7 is much lower than that expected from the relationship of T_N versus the ionic radius of B~(4+) derived from the series of Er_2B_2O_7, while the T_C of Yb_2Pt_2O_7 is the highest among the series of ferromagnetic compounds Yb_2B_2O_7 (B = Sn, Pt, Ti). Given the monotonic variation of the lattice constant as a function of the S-cation size across these two series of R_2B_2O_7 (R = Er, Yb), the observed anomalous values of T_(N,C) in the Pt-based XY pyrochlores imply that another important factor beyond the nearest-neighbor R-R distance is playing a role. In light of the anisotropic exchange interactions J_(ex) = {J_(zz),J_±,J_(±±),J_(z±)} for the S = 1/2 XY pyrochlores, we have rationalized these observations by considering a weakened (enhanced) antiferromagnetic planar J_± (ferromagnetic Ising-like J_(zz)) due to strong Pt 5d-O2p hybridization within the plane perpendicular to the local [111] direction.
机译：我们通过X射线/中子粉末衍射，dc和ac磁化率以及低至70 mK的比热测量报告了两种有效的伪自旋S = 1/2 XY烧绿石Er_2Pt_2O_7和Yb_2Pt_2O_7的高压合成和详细表征。我们发现这两种化合物都在T_（N，C）≈0.3 K处经历了远距离磁跃迁，这取决于它们转变温度的场依赖性，分别归因于Er_2Pt_2O_7和Yb_2Pt_2O_7的反铁磁型和铁磁型顺序以及与其他类似的烧绿石R_2B_2O_7（R = Er，Yb； B = Sn，Ti，Ge）的系统比较。在铁磁性化合物Yb_2B_2O_7系列中，观察到的Er_2Pt_2O_7的T_N远低于根据T_N与来自Er_2B_2O_7系列的B〜（4+）的离子半径的关系所预期的值，而Yb_2Pt_2O_7的T_C最高。 B = Sn，Pt，Ti）。给定在这两个系列的R_2B_2O_7（R = Er，Yb）上晶格常数随S-阳离子大小变化的单调变化，则在基于Pt的XY烧绿石中观察到的T_（N，C）异常值暗示最近邻居RR距离之外的另一个重要因素正在发挥作用。鉴于S = 1/2 XY烧绿石的各向异性交换相互作用J_（ex）= {J_（zz），J_±，J_（±±），J_（z±）}，我们通过考虑以下因素使这些观察合理化由于在垂直于局部[111]方向的平面内发生了强Pt 5d-O2p杂化作用，因此减弱了（增强的）反铁磁平面J_±（类似于铁磁Ising的J_（zz））。

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  • 来源
    《Physical review》 |2016年第1期|014443.1-014443.10|共10页
  • 作者

    Y. Q. Cai; Q. Cui; X. Li; Z. L. Dun; J. Ma; C. dela Cruz; Y. Y. Jiao; J. Liao; P. J. Sun; Y. Q. Li; J. S. Zhou; J. B. Goodenough; H. D. Zhou; J.-G. Cheng;

  • 作者单位

    Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;

    Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;

    Materials Science and Engineering Program and Texas Materials Institute, University of Texas at Austin, Austin, Texas 78712, USA;

    Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA;

    Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA;

    Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA;

    Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;

    Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;

    Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;

    Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;

    Materials Science and Engineering Program and Texas Materials Institute, University of Texas at Austin, Austin, Texas 78712, USA;

    Materials Science and Engineering Program and Texas Materials Institute, University of Texas at Austin, Austin, Texas 78712, USA;

    Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA;

    Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;

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