Electronic States of Collosal Magnetoresistive Manganites La_0.67Pb_0.33Mn_1-xFe_xO₃from Photoemission Spectroscopy

Abstract

The electron photoemission spectra of valence bands and core-level states of manganese perovskite La0.67Pb0.33(Mn1−xFex)O3 with x = 0, 0.01, 0.03, 0.06, 0.10 and 0.15 were measured by the X-ray and Ultraviolet Photoemission Spectroscopy (XPS and UPS) below and above the metal-insulator transition. From analysis of the Mn 2p core-level spectra the ratio Mn 3+ /Mn 4+ was calculated as a function of the iron content. Comparison of the valence band spectrum with band structure calculations and with the high-resolution spectra measured at synchrotron radiation for Ca-, Ba-and Ce-substituted manganites revealed the strong hybridisation of Mn 3d and of O 2p states between −3 eV and −7 eV, and no estimated oxygen states between 0 eV and −2 eV where the Mn-3d states play a predominant role. The composition dependent insulating energy gaps were measured at room temperature. Reasons for the behaviour were discussed taking into account previous analysis of XPS/UPS spectra of other manganese perovskites.

Electronic Band Structure and Photoemission States of La2/3Pb1/3MnO3

“…In our previous study [20] the half metallic gaps in this system were measured and estimated in room temperature to be from 1.7 to 2.0 eV which is in very good agreement with these calculations. In the same work an open question was which states form the pronounced spectral density in the conduction band from −12 eV to −9 eV.…”

“…4). The com- parison of calculated band electron photoemission spectrum and the ultraviolet electron photoemission (UPS) spectrum measured in our paper [20] is shown in Fig. 5.…”

Structural change from Pbnm to R3̅c phase with varying Fe/Mn content in (1-x) LaFeO3.xLaMnO3 solid solution leading to modifications in octahedral tilt and valence states

“…Satellite peaks are observed when photoelectron interact with outermost 3d electron (closely packed multiplet split-3d electron). As a result the outermost 3d electron after gaining energy from photoelectron get excited to higher vacant state [70]. The Mn2p satellite intensity decreases for 0.125≤x≤0.5, and thereafter increases for 0.5≤x≤0.875.…”

Physical properties of La1−xPbxMnO3 perovskites with 0.24≤x≤0.40

“…9a. The 2p 3/2 and 2p 1/2 peaks are the result of overlapping lines due to Mn 4+ , Mn 3+ and Pb4p 3/2 [18]. The binding energies increase little as the Mn 4+ content is higher.…”