Carrier Density Collapse and Colossal Magnetoresistance in Doped Manganites

TL;DR

This paper uncovers a ferromagnetic transition in doped manganites involving carrier density collapse, explaining their resistivity peak and colossal magnetoresistance through polaronic carrier interactions and magnetic field sensitivity.

Contribution

It introduces a new understanding of the ferromagnetic transition driven by electron-phonon coupling and carrier pairing, linking it to colossal magnetoresistance phenomena.

Findings

Carrier density collapses during the transition.

Transition order depends on exchange interaction strength.

Collapse explains resistivity peak and magnetoresistance.

Abstract

A novel ferromagnetic transition, accompanied by carrier density collapse, is found in doped charge-transfer insulators with strong electron-phonon coupling. The transition is driven by an exchange interaction of polaronic carriers with localized spins; the strength of the interaction determines whether the transition is first or second order. A giant drop in the number of current carriers during the transition, which is a consequence of bound pairs formation in the paramagnetic phase close to the transition, is extremely sensitive to an external magnetic field. This carrier density collapse describes the resistivity peak and the colossal magnetoresistance of doped manganites.