Element-specific insight into ferromagnetic stability in UCoGe revealed by soft X-ray magnetic circular dichroism

Takeda, Yukiharu   ; Pospil, J.*; Yamagami, Hiroshi; Yamamoto, Etsuji  ; Haga, Yoshinori   

We investigated the element-specific electronic states and magnetic properties of ferromagnetic superconductor UCoGe and Ru-substituted U(CoRu)Ge using soft X-ray magnetic circular dichroism (XMCD) experiments. YCoGe, a nonmagnetic compound without the 5 electrons, was also examined as a reference material. The shapes of the XMCD spectra of UCoGe at the U and Ge edges are indistinguishably similar to those of U(CoRu)Ge. On the other hand, the XMCD spectral shape at the Co edge is very peculiar and is changed by the existence of the U 5 electrons and the Ru substitution. From the sum rule analysis for the XMCD spectra, it was found that the magnetic moments of the U 5 and Co 3 electrons in UCoGe and U(CoRu)Ge are aligned in the same direction under the present experimental conditions; = 5.5 - 50 K and = 0 - 10 T. Furthermore, even in the case of YCoGe, the Co 3 electrons have a large orbital magnetic moment, suggesting that the Co 3 electrons in these compounds are in a low symmetric electronic environment originally. Through the - and -dependence of the XMCD intensity, it was revealed that the magnetic properties at the Co site are not simply induced by the magnetism at the U site and that the Co 3 electrons play an important role in the stability of ferromagnetism.