Ferromagnetic insulator induced by Peierls instability at orbital order transition

Abstract

The origin of the ferromagnetic insulating state of La7/8Sr1/8MnO3 is investigated. Based on the tight-binding model, it is shown that this state can be attributed to the Peierls instability arising from the interplay of spin and orbital ordering. The importance of the hole–orbiton–phonon intercoupling in doped manganites is revealed. This picture explains well the recent experimental finding of re-entrance of the ferromagnetic metal state at low temperatures (Phys. Rev. Lett.96 097201).