Photoemission study of RCo2 (R=Ce, Pr, Nd).

We report the photoemission spectroscopy (PES) studies on [ital R]Co[sub 2] ([ital R]=Y, Ce, Pr, Nd). The [ital R] 4f PES spectra of [ital R]Co[sub 2] exhibit double peak structures, in which the spectral weight close to [ital E][sub [ital F]] decreases from CeCo[sub 2] to PrCo[sub 2] and NdCo[sub 2]. The Ce valence in CeCo[sub 2] is estimated to be [similar to]3.2, whereas rare-earth valences in PrCo[sub 2] and NdCo[sub 2] are close to 3+, implying that the contribution from the [ital R] 4f localized moment would be larger in PrCo[sub 2] and NdCo[sub 2]. The Co 3[ital d] spectra are found essentially identical in large energy scales, suggesting that the Co 3[ital d] electronic structures are very similar in [ital R]Co[sub 2] for light rare earths. Weak Co 3[ital d] satellite features are observed about 5 eV below [ital E][sub [ital F]]. The comparison with the band-structure calculations for [ital R]Co[sub 2] shows that the theoretical Co 3[ital d] bandwidths are comparable to the experimental bandwidths, which can be considered to imply a rather delocalized nature of Co 3[ital d] electrons. However, some discrepancies are found in the spectral weight near the satellite emission, which implies that Comore » 3[ital d] correlations are non-negligible. The existence of the non-negligible Co 3[ital d] correlation effects is also supported by the analysis of Co [ital MVV] Auger spectra.« less