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Orbital ordering in La$_{0.5}$Sr$_{1.5}$MnO$_4$ studied by model Hartree-Fock calculation

K. Ebata·T. Mizokawa·A. Fujimori
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Abstract

We have investigated orbital ordering in the half-doped manganite La$_{0.5}$Sr$_{1.5}$MnO$_4$, which displays spin, charge and orbital ordering, by means of unrestricted Hartree-Fock calculations on the multiband $p$-$d$ model. From recent experiment, it has become clear that La$_{0.5}$Sr$_{1.5}$MnO$_4$ exhibits a cross-type $(z^2-x^2/y^2-z^2)$ orbital ordering rather than the widely believed rod-type $(3x^2-r^2/3y^2-r^2)$ orbital ordering. The calculation reveals that cross-type $(z^2-x^2/y^2-z^2)$ orbital ordering results from an effect of in-plane distortion as well as from the relatively long out-of-plane Mn-O distance. For the "Mn$^{4+}$" site, it is shown that the elongation along the c-axis of the MnO$_6$ octahedra leads to an anisotropic charge distribution rather than the isotropic one.

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K. Ebata, T. Mizokawa, A. Fujimori. 2005-11-10. Orbital ordering in La$_{0.5}$Sr$_{1.5}$MnO$_4$ studied by model Hartree-Fock calculation. https://doi.org/10.1103/physrevb.72.233104

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