arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1111.5693cond-mat.str-el
收藏

CeRuSn中的复杂费用排序

Complex charge ordering in CeRuSn

R. Feyerherm, E. Dudzik, S. Valencia, J. A. Mydosh, Y. -K. Huang, W. Hermes, R. Pöttgen

摘要:

在环境温度下,CeRuSn表现出两种类型的Ce离子在金属环境中共存的特殊结构,即三价Ce 3+和中间价Ce(4-x)+。电荷排序产生的基本单斜CeCoAl型结构的沿c轴的单位电池的两倍。在室温以下,观察到具有非常宽的滞后的相变,在各种体性质,如电阻率,磁化率和比热。目前的X射线衍射结果表明,在低温下的CeCoAl型结构的加倍是由一个不明确的调制基态取代。在这种状态下,至少有三个不同的调制周期竞争,其中主导模式接近基本单元的三倍。这种转变伴随着c轴的显著收缩。XANES数据表明Ce的平均价态保持不变,因此观察到的c轴收缩不是由于任何价态转变。我们提出了一个定性的结构模型与修改后的堆叠顺序的Ce 3+和Ce(4-x)+层在各种调制阶段。令人惊讶的是,远低于100 K的调制状态是敏感的X射线照射在同步加速器的光子通量。随着光子通量的顺序10 E12/s,调制的基态可以在几分钟的时间尺度上被破坏,并恢复在室温下观察到的CeCoAl电池的倍增。终态在10 K时是亚稳态。将样品加热到60 K以上再次导致调制状态的恢复。因此,CeRuSn表现出热和X射线诱导的Ce 3 +/Ce(4-x)+电荷有序模式的可逆转变。这种行为在任何已知的金属间化合物中是独特的。

英文摘要:

At ambient temperatures, CeRuSn exhibits an extraordinary structure with a coexistence of two types of Ce ions in a metallic environment, namely trivalent Ce3+ and intermediate valent Ce(4-x)+. Charge ordering produces a doubling of the unit cell along the c-axis with respect to the basic monoclinic CeCoAl type structure. Below room temperature, a phase transition with very broad hysteresis has been observed in various bulk properties like electrical resistivity, magnetic susceptibility, and specific heat. The present x-ray diffraction results show that at low temperatures the doubling of the CeCoAl type structure is replaced by an ill-defined modulated ground state. In this state, at least three different modulation periods compete, with the dominant mode close to a tripling of the basic cell. The transition is accompanied by a significant contraction of the c axis. XANES data suggest that the average Ce valence remains constant, thus the observed c axis contraction is not due to any valence transition. We propose a qualitative structure model with modified stacking sequences of Ce3+ and Ce(4-x)+ layers in the various modulated phases. Surprisingly, far below 100 K the modulated state is sensitive to x-ray irradiation at photon fluxes available at a synchrotron. With photon fluxes of order 10E12/s, the modulated ground state can be destroyed on a timescale of minutes and the doubling of the CeCoAl cell observed at room temperature is recovered. The final state is metastable at 10 K. Heating the sample above 60 K again leads to a recovery of the modulated state. Thus, CeRuSn exhibits both thermally and x-ray induced reversible transformations of the Ce3+/Ce(4-x)+ charge ordering pattern. Such a behavior is unique among any know intermetallic compound.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑