PHOTOEMISSION-STUDY OF VALENCE-ELECTRONS IN LA(CO1-XFEX)(13) (X=0,0.2)

The electronic structure of La(Co-1-Fe-x(x))(13) (x = 0, 0.2) has been investigated by using photoemission spectroscopy. The La 5d and T 3d (T = Fe, Co) partial spectral weights (PSW's) are extracted and compar ed with the calculated angular-momentum-projected densities of states (PLDOS's). No Co 3d satellite is observed, implying a weak Co 3d Coulo mb correlation in this system. La 5d emissions exhibit a weak enhancem ent near the La 4d absorption edge, from which the La 5d PSW's of La(C o1-xFex)(13) (x = 0, 0.2) have been extracted. For a given x in La(Co1 -xFex)(13), the overall features of the La 5d PSW, such as bandwidths and long tails, are rather similar to those of the T 3d PSW, indicatin g large hybridization between the T 3d and La 5d states. The experimen tal Co 3d and La 5d PSW's of LaCo13 show a large disagreement with the calculated PLDOS's. With a substitution of Fe for Co, the PSW's of La (Co1-xFex)(13) remain nearly unchanged between x = 0 and 0.2, which is contradictory to the predicted changes in the PLDOS's obtained in the rigid-band scheme. This finding suggests a breakdown of a simple rigi d-band approximation in La(Co1-xFex)(13), which is probably due to a l arge hybridization bonding between Co and Fe 3d electrons.