Colossal magnetooptical conductivity in doped manganites

TL;DR

This paper explains the colossal magnetooptical conductivity in doped manganites as a result of bipolaron dissociation into polarons under magnetic fields near the ferromagnetic transition, aligning with experimental data.

Contribution

It introduces a bipolaron-based mechanism for the colossal magnetooptical effect in doped manganites, linking it to carrier density collapse and magnetic interactions.

Findings

Colossal change in optical conductivity near ferromagnetic transition

Magnetooptical effect varies with frequency, positive at low and negative at high frequencies

Results align with experimental observations of manganites

Abstract

We show that the current carrier density collapse in doped manganites, which results from bipolaron formation in the paramagnetic phase, leads to a colossal change of the optical conductivity in an external magnetic field at temperatures close to the ferromagnetic transition. As with the colossal magnetoresistance (CMR) itself, the corresponding magnetooptical effect is explained by the dissociation of localized bipolarons into mobile polarons owing to the exchange interaction with the localized Mn spins in the ferromagnetic phase. The effect is positive at low frequencies and negative in the high-frequency region. The present results agree with available experimental observations.