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Valence modulations in CeRuSn

机译：CeRuSn中的价态调制

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摘要

CeRuSn exhibits an extraordinary room temperature structure at 300 K with the coexistence of two types of Ce ions, namely trivalent Ce~(3+) and intermediate-valent Ce~((4-δ)+), in a metallic environment. The ordered arrangement of these two Ce types on specific crystallographic sites results in a doubling of the unit cell along the c axis with respect to the basic monoclinic CeCoAl-type structure. Below room temperature, structural modulation transitions with very broad hysteresis have been reported from measurements of various bulk properties. X-ray diffraction revealed that at low temperatures the doubling of the CeCoAl-type structure is replaced by a different modulated ground state, approximating a near tripling of the basic CeCoAl cell. The transition is accompanied by a significant contraction of the c axis. We present new x-ray absorption near-edge spectroscopy data at the Ce L_3 absorption edge, measured on a freshly cleaved surface of a CeRuSn single crystal. In contrast to our previous report, the new data exhibit small but significant variations as a function of temperature that are consistent with a transition of a fraction of Ce~(3+) ions to the intermediate valence state, analogous to the γ → α transition in elemental cerium, when cooling through the structural transitions of CeRuSn. Such results in a valence-modulated state.
机译：在金属环境中，CeRuSn在300 K下表现出非同寻常的室温结构，并与三价Ce〜（3+）和中价Ce〜（（4-δ）+）两种类型的Ce离子共存。相对于基本单斜CeCoAl型结构，这两种Ce类型在特定晶体学位点上的有序排列导致单位晶胞沿c轴加倍。在室温以下，从各种体积性质的测量中已经报道了具有非常宽的磁滞的结构调制转变。 X射线衍射表明，在低温下，CeCoAl型结构的加倍被不同的调制基态所取代，近似于基本CeCoAl电池的三倍。过渡伴随着c轴的明显收缩。我们提出了在Ce L_3吸收边缘的新X射线吸收近边缘光谱数据，该数据是在CeRuSn单晶的新开裂表面上测得的。与我们之前的报告相反，新数据显示出随温度变化的微小但显着的变化，与一部分Ce〜（3+）离子向中间价态的跃迁相一致，类似于γ→α跃迁。在铈铈中通过CeRuSn的结构转变进行冷却时。这样导致价态调节。

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  • 来源
    《Physical review》 |2014年第4期|041104.1-041104.4|共4页
  • 作者

    R. Feyerherm; E. Dudzik; K. Prokes; J. A. Mydosh; Y.-K. Huang; R. Poettgen;

  • 作者单位

    Helmholtz-Zentrum Berlin fuer Materialien und Energie GmbH, BESSY, 12489 Berlin, Germany;

    Helmholtz-Zentrum Berlin fuer Materialien und Energie GmbH, BESSY, 12489 Berlin, Germany;

    Helmholtz-Zentrum Berlin fuer Materialien und Energie GmbH, 14109 Berlin, Germany;

    Kamerlingh Onnes Laboratory, Leiden Universite, 2300 RA Leiden, The Netherlands;

    Van der Waals-Zeeman Institute, Universite of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands;

    Institute for Inorganic and Analytical Chemistry, Universite of Muenster, 48149 Muenster, Germany;

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  • 正文语种 eng
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  • 关键词

    narrow-band systems; intermediate-valence solids;

    机译：窄带系统;中价固体;

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