On magnetoconductivity of metallic manganite phases and heterostructures

TL;DR

This paper models the magnetoconductivity of metallic manganite phases using the double exchange model, analyzing effects of disorder, phase interfaces, and Jahn-Teller distortions, with implications for experimental superlattice data.

Contribution

It applies the double exchange model to study magnetoconductivity in manganites, incorporating disorder and phase boundary effects, and interprets experimental superlattice data.

Findings

Charge redistribution occurs near phase contacts.

Large screening length of about five atomic distances.

Jahn-Teller distortions significantly influence the A-phase formation.

Abstract

We use the double exchange (DE) model via degenerate orbitals and tight-binding approximation to study the magnetoconductivity of a canted A-phase of pseudo-cubic manganites. It is argued that the model is applicable in a broad concentration range for manganites with the tolerance factor, t, close to one. As for the substitutional disorder, scattering on random Jahn-Teller distortions of MnO6 octahedra is chosen. We emphasize an intimate correlation between the carrier concentration and resistivity value of metallic manganites. Magnetoresistance as a function of magnetization is calculated for a canted A-phase for both in-plane and out-of-plane current directions. A contact between two manganite phases is considered and structure of the transition region near the contact is discussed. Numerical calculations show charge re-distribution near the contact and a large screening length of the order of five inter-atomic distances. We employed our results to interpret data obtained in recent experiments on La0.4Sr0.6MnO3/La0.55Sr0.45MnO3 superlattices. We also briefly discuss the relative importance of the cooperative Jahn-Teller distortions, double exchange mechanism and super-exchange interactions for the formation of the A-phase at increasing Sr concentrations x>0.45 in LSMO to suggest that the Jahn-Teller contraction of octahedra, c/a<1, plays a prevailing role.