Near Fermi level electronic structure ofPr1−xSrxMnO3: Photoemission study

Abstract

In this study, we report the observation of a pseudogap associated with the insulator-metal transition in compositions of Pr1−xSrxMnO3 system with no charge ordering. Our valence band photoemission study shows that the observed shifts in the near Fermi level density of states are abrupt at the Curie transtion and occur over an energy scale of ∼ 1 eV, strongly suggesting that the charge-ordering gap observed earlier in other manganites and the pseudogap observed here may indeed have same origin. These results could be understood within the framework of models based on electronic phase separation where it has been shown that the pseudogap is a generic feature of the mixed-phase compositions. Also, our band structure calculations on Pr0.75Sr0.25MnO3 show the possible existence of half-metallicity in this system.

Valence-band study of Sm0.1Ca0.9−xSrxMnO3 using high-resolution ultraviolet photoelectron spectroscopy

“…The observed features in the spectra ( Fig. 1) are the characteristics of manganites studied earlier [21][22][23][24][25][26][27][28]. However, our present focus here is to investigate the finer variations of the electronic states in the vicinity of the Fermi level.…”

“…Here the density of e g states for x = 0.3 and 0.6 samples almost disappears with the formation of an insulating gap at the Fermi level. Based on earlier reports [22,23,27,28,[30][31][32][33][34] the suppressed density of states at the Fermi level could be due to the disorder/mixed phase (FM metallic and AFM insulating) and is generally described in terms of a pseudogap phase. The pseudogaplike behavior in the Sm 0.1 Ca 0.9−x Sr x MnO 3 system is found to gradually evolve into normal insulating behavior [Figs.…”

Possible origin of photoconductivity in La0.7Ca0.3MnO3

“…22 Figure 1 shows the core-level XPS spectra for the studied sample. The peaks A and B are attributed to the e g ͑͒ and t 2g ͑⌸͒ levels and peak C is due to the O 2p character; [23][24][25][26] and is assigned to the O 2p ͑⌸͒ character. The atomic sensitivity for each element, i.e., La, Ca, Mn, and that of oxygen with respect to Al K␣ ͑1486.6 eV͒ was taken in to account for compositional estimation.…”

Electronic structure of the electron-doped Ca0.86Pr0.14MnO3

“…A discussion on these spectral features can be found in earlier reports. [23][24][25][26][27][28] It should be noted from the figure that with decrease in temperature the intensity of the feature A increases, while that of the features B and C decrease. Temperature dependence of the Mn 3d e g↑ states is more clearly visible in Fig.…”