Hidden relationship between the electrical conductivity and the Mn 2p core-level photoemission spectra in La1-xSrxMnO3

TL;DR

This study reveals a complex relationship between Mn 2p core-level spectra and electrical conductivity in La1-xSrxMnO3, showing that spectral weights do not directly correspond to simple oxidation states but relate to conductivity changes.

Contribution

The paper uncovers the hidden relationship between Mn 2p photoemission spectral features and electrical conductivity, challenging the straightforward interpretation of Mn oxidation states in La1-xSrxMnO3.

Findings

Mn 2p3/2 peak decomposed into four components

Spectral weights do not directly match Mn oxidation states

Sum of specific spectral weights correlates with conductivity

Abstract

Core-level electronic structure of La1-xSrxMnO3 has been studied by x-ray photoemission spectroscopy (XPS). We first report, by the conventional XPS, the well-screened shoulder structure in Mn 2p3/2 peak, which had been observed only by hard x-ray photoemission spectroscopy so far. Multiple-peak analysis revealed that the Mn4+ spectral weight was not proportional to the nominal hole concentration x, indicating that a simple Mn3+/Mn4+ intensity ratio analysis may result in a wrong quantitative elemental analysis. Considerable weight of the shoulder at x=0.0 and the fact that the shoulder weight was even slightly going down from x=0.2 to 0.4 were not compatible with the idea that this weight simply represents the metallic behavior. Further analysis found that the whole Mn 2p3/2 peak can be decomposed into four portions, the Mn4+, the (nominal) Mn3+, the shoulder, and the other spectral weight located almost at the Mn3+ location. We concluded that this weight represents the well-screened final state at Mn4+ sites, whereas the shoulder is known as that of the Mn3+ states. We found that the sum of these two spectral weight has an empirical relationship to the conductivity evolution with x.