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We study a simplified model of the electronic structure of compounds of the type of La$_{1-x}$Sr$_x$MnO$_3$. The model represents each Mn$^{4+}$ ion by a spin S=1/2, on which an electron can be added to produce Mn$^{3+}$. We include two strong intratomic interactions in the Hamiltonian: exchange ($J$% ) and Coulomb ($U$). Finally, to represent the effect of Sr substitution by La in a simple way, we include a distribution of diagonal energies at the Mn sites. Then we use Green function techniques to calculate a mobility edge and the average density of states. We find that according to the amount of disorder and to the concentration of electrons in the system, the Fermi level can cross the mobility edge to produce a metal to insulator transition as the magnetization decreases (increase of temperature). If the disorder is large, the system remains insulating for all concentrations. Concentrations near zero or one favor the insulating state while intermediate values of concentration favor the metallic state.
The crystal and magnetic structure of La_{1-x}Sr_{1+x}MnO_4 (0<x<0.7) has been studied by diffraction techniques and high resolution capacitance dilatometry. There is no evidence for a structural phase transition like those found in isostructural cup
We use a model previously formulated based on the double exchange mechanism and diagonal disorder to calculate magnetization and conductivity for La_{1-x}Sr_xMnO_3 type crystals as a function of temperature. The model represents each Mn^{4+} ion by a
By using laboratory x-ray photoemission spectroscopy (XPS) and hard x-ray photoemission spectroscopy (HX-PES) at a synchrotron facility, we report an empirical semi-quantitative relationship between the valence/core-level x-ray photoemission spectral
We measured thermal conductivity, k, thermoelectric power, S, and dc electric conductivity, sigma, of La_{5/8-x}Pr_{x}Ca_{3/8}MnO_{3}, showing an intricate interplay between metallic ferromagnetism (FM) and charge ordering (CO) instability. The chang
We present the electronic structure of Sr_{1-(x+y)}La_{x+y}Ti_{1-x}Cr_{x}O_{3} investigated by high-resolution photoemission spectroscopy. In the vicinity of Fermi level, it was found that the electronic structure were composed of a Cr 3d local state