Dimensional crossover and the magnetic transition in electron doped manganites

TL;DR

This paper presents a microscopic model explaining the magnetic phase transition and metal-insulator transition in electron-doped manganites, highlighting the role of orbital degrees of freedom and Fermi surface topology.

Contribution

It introduces a novel microscopic model that elucidates the magnetic transition mechanism and the associated dimensional crossover in electron-doped manganites.

Findings

The model explains the G-AF to C-AF transition with increasing doping.

It accounts for the metal-insulator transition via dimensional crossover.

Theoretical results match experimental data on specific heat and spin canting.

Abstract

We introduce a microscopic model for electron doped manganites that explains the mechanism of the observed transition from $G$-type antiferromagnetic ($G$-AF) to $C$-type antiferromagnetic ($C$-AF) order under increasing doping by double exchange mechanism. The model unravels the crucial role played by $e_g$ orbital degrees of freedom and explains the observed metal-to-insulator transition by a dimensional crossover at the magnetic phase transition. The specific heat and the spin canting angle found for the $G$-AF phase agree with the experimental findings. As a surprising outcome of the theory we find that spin canting is suppressed in the $C$-AF phase, in agreement with the experiment, due to the Fermi surface topology.