HIGH-ENERGY MAGNETIC SCATTERING FROM A TYPE-II SUPERCONDUCTOR AND FLUCTUATING-VALENCE COMPOUND - CERU2

We report observations of very high-energy magnetic scattering from Ce Ru2 (T-c similar to 6.2 K) relative to LaRu2 (T-c similar to 4.4 K). T he spectral form and intensity of the magnetic response suggests that the 4f electron in CeRu, is essentially localised with a 4f-occupancy of similar to 0.75 (+/- 0.1). The magnitude of the characteristic ener gy of similar to 510 (+/- 50) meV deduced from a fit using a single-io n spectral function is the highest recorded to date. The present obser vations are consistent with a partial delocalisation of the 4f electro n and may appear at variance with the calculated 4f band structures as well as de Haas-van Alphen measurements on CeRu2. They are, neverthel ess, in good accord with X-ray absorption (L-III edge), photoemission, and inverse photoemission (BIS) data. (C) 1998 Elsevier Science B.V. All rights reserved.