X-ray photoemission and magnetometric studies of valence changes in Ce(Cu 1- xNi x) 4Ga

The compounds Ce(Cu _{1- x}Ni _x) ₄Ga crystallize in the hexagonal CaCu ₅-type structure for the whole doping range 0≤ x≤1. The border compounds CeCu ₄Ga and CeNi ₄Ga represent a heavy fermion and fluctuating valence systems, respectively. We report on the studies of the valence evolution in Ce(Cu _{1- x}Ni _x) ₄Ga employing the X-ray photoemission spectroscopy (XPS) and magnetic susceptibility measurements. The photoemission of the Ce 3d peaks shows a gradual decrease of the occupation of the f states with Ni content. Simultaneously, the hybridization strength and the low temperature magnetic susceptibility are reduced. Within the valence band spectrum a transition from the dominance of the Cu 3d to the dominance of the Ni 3d states is well visible with the traces of the Ce 4f ¹ states for up to x=0.5.