Electronic Properties of Fully Strained La_1–xSr_xMnO₃ Thin Films Grown by Molecular Beam Epitaxy (0.15 ≤ x ≤ 0.45)

Abstract

The structural, electronic, and magnetic properties of Sr-hole-doped epitaxial La 1– x Sr x MnO 3 (0.15 ≤ x ≤ 0.45) thin films deposited using the molecular beam epitaxy technique on 4° vicinal STO (001) substrates are probed by the combination of X-ray diffraction and various synchrotron-based spectroscopy techniques. The structural characterizations evidence a significant shift in the LSMO (002) peak to the higher diffraction angles owing to the increase in Sr doping concentrations in thin films. The nature of the LSMO Mn mixed-valence state was estimated from X-ray photoemission spectroscopy together with the relative changes in the Mn L 2,3 edges observed in X-ray absorption spectroscopy (XAS), both strongly affected by doping. CTM4XAS simulations at the XAS Mn L 2,3 edges reveal the combination of epitaxial strain, and different MnO 6 crystal field splitting give rise to a peak at ∼641 eV. The observed changes in the occupancy of the e g and the t 2g orbitals as well as their binding energy positions toward the Fermi level with hole doping are discussed. The room-temperature magnetic properties were probed at the end by circular dichroism.

Impact of thermal gas treatment on the surface modification of Li-rich Mn-based cathode materials for Li-ion batteries

“…The Mn 3+ and Mn 7+ states were treated with D 4h symmetry to account for Jahn-Teller distortion, while the Mn 2+ and Mn 4+ states were considered to have octahedral (O h ) symmetry. 75,76 The Mn L 3,2 edge of Mn 7+ was shifted by 4.9 eV to lower photon energies for the peak position at 645 eV in accordance with the experimental data, ref. 31 The parameters used for the simulations are outlined in Table S1, ESI.…”

Direct determination of Mn valence states in mixed‐valent manganates by photoluminescence spectroscopy

“…Both XPS 42 and XAS 43 studies have been carried out to correlate electrical and magnetic behavior with lattice Mn composition for the entire Sr doping series of LSMO. However, experimental results show discrepancies between the expected ferromagnetic and the actual paramagnetic insulating behaviors as a function of doping, which has been attributed to the uncertainty in the lattice Mn III to Mn IV concentration (determined through XPS multiplet‐peak fitting) or the La/Sr/Mn stoichiometry 44,45 . Here, we show that PL spectroscopy can be very advantageous in the accurate determination of Mn cation composition of LSMO.…”

Structure and magnetic properties of epitaxial Sr-LaMnO3 thin films obtained by polymer assisted deposition

“…This distorted perovskite structure consists of corner-sharing MnO 6 octahedra and La (Sr) cations occupying the 12-fold coordination site formed in the center of eight such octahedra [22]. In theory, La-manganite can be considered as a structure derived from the elementary cubic cell with a lattice parameter of ~ 3.944 Å [23], where La 3+ and Mn 3+ are slightly displaced from their ideal positions, but the precise de nition of phase is usually complicated. Thus, for simplicity, the structure of La 1 −…”