Electronic structure of A- and B-site doped lanthanum manganites: A combined X-ray spectroscopic study

Abstract

The electronic properties of a series of colossal magnetoresistance (CMR) compounds, namely LaMnO3, La1-x,Ba,,xMnO3 (0.2 <= x <= 0.55), La0.76Ba0.24Mn0.84CO0.16O3, and La0.76Ba0.24Mn0.78Ni0.22O3, have been investigated in a detailed spectroscopic study. A combination of X-ray photoelectron spectroscopy (XPS), X-ray emission spectroscopy (XES), X-ray absorption spectroscopy (XAS), and resonant inelastic X-ray scattering (RIXS) was used to reveal a detailed picture of the electronic structure in the presence of Ba, Co, and Ni doping in different concentrations. The results are compared with available theory. The valence band of La1-x,BaxMnO3 (0 <= x <= 0.55) is dominated by La 5p, Mn 3d, and 0 2p states, and strong hybridization between Mn 3d and 0 2p states is present over the whole range of Ba concentrations. Co-doping at the Mn site leads to an increased occupancy of the e(g) states near the Fermi energy and an increase in the XPS valence band intensity between 0.5 and 5 eV, whereas the Ni-doped sample shows a lower density of occupied states near the Fermi energy. The Ni d states are located in a band spanning the energy range of 1.5-5 eV. XAS spectra indicate that the hole doping leads to mixed Mn 3d-O 2p states. Furthermore, RIXS at the Mn L edge has been used to probe d-d transitions and charge-transfer excitations in La1-x,Ba,,xMnO3.