Harima Institute, The Institute of Physical and Chemical Research (RIKEN), Sayo, Hyogo 679-5148, Japan.
Phys Rev Lett. 2011 Oct 21;107(17):177203. doi: 10.1103/PhysRevLett.107.177203. Epub 2011 Oct 19.
We have investigated the temperature and pressure dependency of the electronic structure of Yb-filled skutterudites, YbFe(4)Sb(12) and Yb(0.88)Fe(4)Sb(12), using x-ray absorption and emission spectroscopies. An anomalous increase of the Yb valence, which is beyond the conventional Anderson model picture, is found to coincide with the onset of the ferromagnetic order in the x=0.88 sample below 20 K. In contrast, the nearly stoichiometric YbFe(4)Sb(12) is paramagnetic down to 2 K and the Yb valence is independent of temperature. This evidences a close interplay between the magnetic instability of the Fe 3d electrons and valence instability of the Yb 4f electrons. Under pressure, a sudden increase in the valence is found to occur around 13 GPa for YbFe(4)Sb(12) and 17 GPa for Yb(0.88)YbFe(4)Sb(12).
我们使用 X 射线吸收和发射光谱研究了 Yb 填充的 skutterudites（YbFe(4)Sb(12)和 Yb(0.88)Fe(4)Sb(12)）的电子结构随温度和压力的变化。我们发现，在 x=0.88 样品中，当温度低于 20 K 时，铁磁序开始出现，Yb 的价态会出现异常增加，超出了传统的安德森模型的描述。相比之下，几乎化学计量比的 YbFe(4)Sb(12)在 2 K 以下仍保持顺磁态，Yb 的价态与温度无关。这表明 Fe 3d 电子的磁不稳定性和 Yb 4f 电子的价不稳定性之间存在紧密的相互作用。在压力下，我们发现 YbFe(4)Sb(12)在约 13 GPa 处和 Yb(0.88)Fe(4)Sb(12)在约 17 GPa 处，价态会突然增加。
