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Coulomb correlation and magnetic ordering in double-layered manganites: LaSr$_2$Mn$_2$O$_7$

Julia E. Medvedeva·Vladimir I. Anisimov·Michael A. Korotin·Oleg N. Mryasov·Arthur J. Freeman
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Abstract

A detailed study of the electronic structure and magnetic configurations of the 50 % hole-doped double layered manganite LaSr$_2$Mn$_2$O$_7$ is presented. We demonstrate that the on-site Coulomb correlation (U) of Mn d electrons {\it (i)} significantly modifies the electronic structure, magnetic ordering (from FM to AFM), and interlayer exchange interactions, and {\it (ii)} promotes strong anisotropy in electrical transport, reducing the effective hopping parameter along the {\it c} axis for electrically active $e_g$ electrons. This findng is consistent with observations of anisotropic transport -- a property which sets this manganite apart from conventional 3D systems. A half-metallic band structure is predicted with both the LSDA and LSDA+U methods. The experimentally observed A-type AFM ordering in LaSr$_2$Mn$_2$O$_7$ is found to be energetically more favorable with U $\geq$ 7 eV. A simple interpretation of interlayer exchange coupling is given within double and super-exchange mechanisms based on the dependencies on U of the effective exchange parameters and $e_g$ state sub-band widths.

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Julia E. Medvedeva, Vladimir I. Anisimov, Michael A. Korotin, Oleg N. Mryasov, Arthur J. Freeman. 2001-04-18. Coulomb correlation and magnetic ordering in double-layered manganites: LaSr$_2$Mn$_2$O$_7$. https://doi.org/10.1016/s0304-8853(01)00487-5

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