Magnetic structure of low electron density manganites

Abstract

A magnetic phase diagram of the ground state of layered perovskite manganites is studied in a mean-field approximation for a two-orbital double exchange model with the superexchange interaction between localized spins and Jahn-Teller effect. We take into account the G-type and C-type spin alignment and their canted spin ordering. It is shown that with increasing electron dopant the ground state changes from the G-type state to ferromagnetic state via a G-type canted spin state. The C-type state appears only for the intermediate electron dopant with stronger superexchange interaction. The Jahn-Teller distortion stabilizes ${3y}^{2}\ensuremath{-}{r}^{2}$ orbital ordering in the C-type state while ${x}^{2}\ensuremath{-}{y}^{2}$ ordering occurs in other cases. It is also shown that rather complex electronic phase separation occurs, which is compared with experimental observations.