Mechanism of disappearance of magnetic moment of Ni in relation with Rare Earths, especially with heavy fermion element of Ce

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In this study, we have aimed at making clear the electronic states of CeNi, which is one of the most famous "heavy fermion" compound systems, mainly from the view point of magnetic properties. It is well-known that the CeNi has no magnetic order and the Ni in CeNi is non-magnetic. On the other hand, the GdNi, which has the same crystal-structure as that of CeNi, is revealed to be a ferri-magnet and the Ni in GdNi does retain magnetic moment stemming from 3d electrons. It follows that in (Ce_<1-X>Gd_X) Ni system, the Ni is expected to change its electronic state (of 3d) from non-magnetic state to magnetic one according to the Gd content and the study of the transformation of this (3d) electronic state does give us important clues to understand the mechanism of appearance and disappearance of magnetism. Regarding to Ce, the same thing is expected.What we have carried out and found in these three years is summarized as follows ; (1) we have prepared 6 kinds of single crystals (Gd=0.03, 0.10, 0.15, 0.20, 0.50, 0.80), (2) we have measured magnetic properties for 6 contents of Gd and analyzed using molecular field analysis, (3) in Gd=0.03-0.20, the exchange interaction between Gd and Gd JGd-Gd i.e. RKKY interaction is considerably suppressed, (4) soft X-ray MCD measurement was carried out for Gd=0.8 at SPring-8 and some interesting results were obtained.