Magnetic Phases of Electron-Doped Manganites

G. Venketeswara Pai

doi:10.1103/PhysRevB.63.064431

paper

Magnetic Phases of Electron-Doped Manganites

arXiv:cond-mat/0011273 · doi:10.1103/PhysRevB.63.064431

Abstract

We study the anisotropic magnetic structures exhibited by electron-doped manganites using a model which incorporates the double-exchange between orbital ly degenerate $e_{g}$ electrons and the super-exchange between $t_{2 g}$ electrons with realistic values of the Hund's coupling( $J_{H}$ ), the super-exchange coupling( $J_{A F}$ ), and the bandwidth( $W$ ). We look at the relative stabilities of the G, C and A type antiferromagnetic ph ases. In particular we find that the G-phase is stable for low electron doping as seen in experiments. We find good agreement with the experimentally observed magnetic phase diagrams of electron-doped manganites ( $x > 0.5$ ) such as Nd $_{1 - x}$ Sr $_{x}$ MnO $_{3}$ , Pr $_{1 - x}$ Sr $_{x}$ MnO $_{3}$ , and Sm $_{1 - x}$ Ca $_{x}$ MnO $_{3}$ . We can also explain the experimentally observed orbital structures of the C a nd A phases. We also extend our calculation for electron-doped bilayer manganites of the form R $_{2 - 2 x}$ A $_{1 + 2 x}$ Mn $_{2}$ O $_{7}$ and predict that the C-phase will be absent in t hese systems due to their reduced dimensionality.

7 .ps files included. To appear in Phys. Rev. B (Feb 2001)

Magnetic Phases of Electron-Doped Manganites

Abstract

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