Experimental examination of the variation in Fermi surfaces of heavy-electron compounds around quantum critical points

为了了解重费米子Ce化合物的4f电子从巡游到定域性质的跃迁，我们利用同步辐射装置Spring8进行了软X射线能谱实验，研究了磁有序边界附近的电子结构变化。CeRu_2(Si，Ge)_2体系的软X射线磁性圆二色谱(XMCD)实验揭示了CeRu_2(Si，Ge)_2体系的Ce4f电子态从顺磁态向磁有序态转变的趋势。(Ce，Gd)Ni系统的XMCD实验通过元素特异性观测发现了Ce4f电子的反常磁性行为。

To understand the transition of 4f electrons of heavy-Fermion Ce compounds from the itinerant to the localized natures, we have performed soft X-ray spectroscopy experiments for the study of electronic structure variation near the boundary of magnetic ordering, by using the synchrotron radiation facility SPring-8. The soft X-ray magnetic circular dichroism (XMCD) experiments for the CeRu2(Si,Ge)2 system have revealed the tendency of variation in the Ce 4f electronic states on going from the paramagnetic states to the magnetically ordered states. The XMCD experiments for the (Ce,Gd)Ni system have discovered anomalous magnetic behaviors of Ce 4f electrons by element specific observations.