Dynamical mean field theory for transition temperature and optics of CMR manganites

TL;DR

This paper develops a combined theoretical approach using dynamical mean field theory and band structure calculations to study transition temperature and optical properties of CMR manganites, challenging previous estimates and interpretations.

Contribution

It introduces a novel combined method to accurately model magnetic and optical properties of CMR manganites, revealing new insights into their magnetic interactions and questioning existing theories.

Findings

Previous T_c estimates were inaccurate.

Hund's coupling is approximately 1.5 eV.

Magnetic-order effects may not drive colossal magnetoresistance.

Abstract

A tight binding parametrization of local spin density functional band theory is combined with a dynamical mean field treatment of correlations to obtain a theory of the magnetic transition temperature, optical conductivity and T=0 spinwave stiffness of a minimal model for the pseudocubic metallic $CMR$ manganites such a $La_{1-X}Sr_{x}MnO_{3}$. The results indicate that previous estimates of $T_{c}$ obtained by one of us (Phys. Rev. \textbf{B61} 10738-49 (2000)) are in error, that in fact the materials are characterized by Hunds coupling $J\approx 1.5eV$, and that magnetic-order driven changes in the kinetic energy may not be the cause of the observed 'colossal' magnetoresistive and multiphase behavior in the manganites, raising questions about our present understanding of these materials.