The electronic structure of La(${\mathrm{Co}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Fe}}_{\mathit{x}}$${)}_{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 compared with the calculated angular momentum projected densities of states (PLDOS’s). No Co 3d satellite is observed, impling a weak Co 3d Coulmb correlation in this system. La 5d emissions exhibit a weak enhancement near the La 4d absorption edge, from which the La 5d PSW’s of La(${\mathrm{Co}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Fe}}_{\mathit{x}}$${)}_{13}$ (x=0,0.2) have been extracted. For a given x in La(${\mathrm{Co}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Fe}}_{\mathit{x}}$${)}_{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, indicating a large hybridization between the T 3d and La 5d states. The experimental Co 3d and La 5d PSW’s of ${\mathrm{LaCo}}_{13}$ show a large disagreement with the calculated PLDOS’s. With a substitution of Fe for Co, the PSW’s of La(${\mathrm{Co}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Fe}}_{\mathit{x}}$${)}_{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 rigid-band approximation in La(${\mathrm{Co}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Fe}}_{\mathit{x}}$${)}_{13}$, which is probably due to a large hybridization bonding between Co and Fe 3d electrons.

• Received 3 March 1995

DOI:https://doi.org/10.1103/PhysRevB.52.4360