We have studied the chemical potential shift and changes in the electronic density of states near the Fermi level (E F) as functions of temperature and carrier concentration in Pr 1-x Ca x MnO 3 (PCMO) and Nd 1-x Sr x MnO 3 (NSMO) by measurements of photoemission spectra. Suppression of the chemical potential shift as a function of carrier concentration has been observed in PCMO and NSMO near and in the composition range where the CE-type antiferromagnetic charge-ordered (CO) phase appears at low temperatures. This result indicates that there is charge self-organization on a microscopic scale such as stripe formation in this composition range. In the ferromagnetic metallic phase of NSMO, we found a large temperature-dependent chemical potential shift at low temperatures and attributed this to double-exchange mechanism. Suppression of the temperature-dependent chemical potential shift near Curie temperature was observed, possibly associated with the formation of correlated polarons. In the valence band near the E F of PCMO, spectral weight was transferred with hole doping, leading to a finite intensity at E F even in the paramagnetic insulating phase above the CO phase for x ≳ 0.3, and as the temperature was lowered, a clear gap opening was observed in the CO phase.
- Charge order
- Phase separation
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics