Thermodynamics of the Double Exchange Systems

Abstract

This article gives a comprehensive review on the recent studies of the double exchange systems using non-perturbative approaches; the dynamical mean-field theory and the Monte Carlo method. Investigations beyond mean-field type treatments are described. Taking into account strong spin fluctuations which create large changes in conduction electron structure, finite temperature properties as well as dynamics of the system are calculated. Comparisons with experimental data for colossal magnetoresistance manganites are made. We show that high Curie temperature (Tc) compounds, e.g. (La,Sr)MnO3, are canonical double-exchange systems. Properties of other compounds with lower Tc are discussed in relation to inhomogeneities of the system including the issue of phase separation.