Giant dielectric permittivity and magneto-capacitance effects in low doped manganites

TL;DR

This paper explores how phase separation and Coulomb interactions in low-doped manganites lead to giant dielectric permittivity and magneto-capacitance effects near magnetic phase transitions.

Contribution

It provides a phenomenological phase diagram explaining the formation of inhomogeneous charged states responsible for these effects.

Findings

Giant dielectric permittivity occurs near the magnetic transition.

Long-range Coulomb forces induce inhomogeneous charged states.

Large dielectric function enables magnetoelectric effects.

Abstract

The effect of giant dielectric permittivity due to phase separation accompanied by charged inhomogeneities in low-doped manganites is discussed. The effect appears in the vicinity of the second-order magnetic phase transition and is caused by long-range Coulomb forces. The long-range Coulomb interaction is responsible for the formation of inhomogeneous charged states and determines their characteristic length scales. We derive the phase diagram of the inhomogeneous charged states in the framework of the phenomenological theory of phase transitions. The large value of the static dielectric function reduces the characteristic value of the Coulomb energy of the inhomogeneous state and makes the appearance of the magnetoelectric effect possible. We discuss the formation of a state with giant dielectric permittivity and magneto-capacitance effects in that case.