Phase separation in double exchange systems

TL;DR

This paper investigates phase separation in double exchange ferromagnetic systems, revealing temperature-dependent instability and significant effects on thermopower near the Curie temperature due to bandwidth variations.

Contribution

It demonstrates the tendency for phase separation near T_c and explains the impact of spin disorder on electronic bandwidth and thermopower.

Findings

System unstable to phase separation near T_c

Bandwidth decreases with doping and spin disorder

Thermopower peaks near T_c with opposite sign to rigid band predictions

Abstract

Ferromagnetic systems described by the double exchange model are investigated. At temperatures close to the Curie temperature, and for a wide range of doping levels, the system is unstable toward phase separation. The chemical potential decreases upon increasing doping, due to the significant dependence of the bandwidth on the number of carriers. The reduction of the electronic bandwidth by spin disorder leads to an enormously enhanced thermopower which peaks near T_c, with a sign opposite that predicted by a rigid band model.