Electron- and hole-doping effects on the electronic structure of manganite studied by x-ray absorption spectroscopy

Abstract

The electronic structures of hole-doped La0.7Ca0.3MnO3 and electron-doped La0.7Ce0.3MnO3 manganites are investigated by x-ray absorption near-edge structure spectroscopy at the O and Mn K-, and Mn L3,2-edges. The Mn K- and L3,2-edge results show that Ce dopants increase the occupation of the Mn 4p and majority-spin eg orbitals and reduce the positive effective charge of some Mn ions. However, Ce doping also induces holes in O 2p derived states. As for La0.7Ca0.3MnO3, in contrast to previous understanding that Ca doping converts some Mn ions into the Mn4+ state, we find that Ca dopants actually increase the number of majority-spin eg electrons. We find instead that the holes created by Ca dopants are in the O 2p derived states.

Intrinsic ferromagnetism and magnetic anisotropy in Gd-doped ZnO thin films synthesized by pulsed spray pyrolysis method

“…The spectra were normalized to the incident photon flux, and vacuum of the experimental chamber was better than 1 ϫ 10 −8 Torr. 23,24 Recently, a similar pre-edge feature were observed in Nd doped ZnO, 13 Cu doped ZnO, 26 and Mn doped ZnO, 27 and have been assigned to doping-induced lower-lying O 2p "impurity" states. [22][23][24] The O K edge is essentially described as a one-particle process ͑direct transitions from O 1s to O p levels͒, and is closely related to the empty O p density of states.…”

“…23,28,29 Figure 6 displays the NEXAFS spectra at M 5 edge of Gd-doped ZnO. The NEXAFS at M 5,4 -edge probes directly the inner 4f configuration ͑3d 5/2,3/2 → 4f transitions͒.…”

Optimizing the synthesis of cobalt-based catalysts for the selective growth of multiwalled carbon nanotubes under industrially relevant conditions

“…The near-edge X-ray analysis of fine structure spectroscopy (NEXAFS) of the sharp L-edge is a sensitive probe for the surface-near region and can resolve different oxidation states of mixed valent ions [56,57] . The state of the Mn ions during reduction and after growth reaction were investigated in order to provide information on the chemical state and the electronic structure of the Mn.…”

Influence of Ce doping on electrical and thermal properties of La0.7−xCexCa0.3MnO3 (0.0≤x≤0.7) manganites

“…[1][2][3], or tetravalent such as Ce, Sn, Te, etc. [4][5][6][7][8][9][10][11][12][13][14][15]. Both classes of these materials exhibit a rich phase diagram as a function of temperature, magnetic field and doping, and illustrate the metal-insulator transition as well as the phenomenon of colossal magnetoresistance (CMR).…”

“…The physical properties such as electrical resistivity, magnetization, susceptibility, Seebeck coefficient, specific heat and thermal conductivity, etc., have been studied extensively in the framework of double exchange (DE) interaction for the hole doped manganites so far [3]. On the other hand, it has been recognized that the tetravalent cation doping drives the valence state of Mn 3 þ in the parent compound into a mixed-valence state of Mn 3 þ and Mn 2 þ , i.e., possible electron-doped systems with electric configurations of the type: t 3 2g e 2 g and t 3 2g e 1 g [4], and it is possible to utilized such electron-doped systems as a functional spintronics devices in the future. These studies on the electron doped systems demonstrated that the basic physics in terms of Hund's rule coupling between e g electrons and t 2g core electrons and the Jahn-Teller (JT) effect due to Mn 3 þ JT ions can operate in the electron doped manganites as well [4][5][6][7][8][9][10][11][12][13][14][15].…”