Chemical potential shift and spectral-weight transfer in Pr1-x Cax Mn O3 revealed by photoemission spectroscopy

We have studied the chemical potential shift and changes in the electronic density of states near the Fermi level (EF) as a function of carrier concentration in Pr1-x Cax Mn O3 (PCMO, 0.2≤x≤0.65) through the measurements of photoemission spectra. The results showed that the chemical potential shift was suppressed for x 0.3, where the charge-exchange (CE) type antiferromagnetic charge-ordered state appears at low temperatures. We consider this observation to be related to charge self-organization such as stripe formation on a microscopic scale in this composition range. Together with the previous observation of monotonous chemical potential shift in La1-x Srx Mn O3, we conclude that the tendency toward the charge self-organization increases with decreasing bandwidth. In the valence band, spectral weight of the Mn 3d eg electrons in PCMO was transferred from ∼1 eV below EF to the region near EF with hole doping, leading to a finite intensity at EF even in the paramagnetic insulating phase for x 0.3, probably related with the tendency toward charge self-organization. The finite intensity at EF in spite of the insulating transport behavior is consistent with fluctuations involving ferromagnetic metallic states.