Spiral phase and phase separation of the double exchange model in the large-S limit

TL;DR

This paper analyzes the phase diagram of the double exchange model in large-S limit, revealing the stability of spiral states and phase separation phenomena in different coupling regimes at zero temperature.

Contribution

It provides a detailed study of the phase diagram, identifying conditions under which spiral states are stable or lead to phase separation in the double exchange model.

Findings

Spiral states have lower energy than canted antiferromagnetic states.

Phase separation occurs at small doping due to negative compressibility.

The nature of phase separation depends on Hund coupling strength.

Abstract

The phase diagram of the double exchange model is studied in the large-S limit at zero temperature in two and three dimensions. We find that the spiral state has lower energy than the canted antiferromagnetic state in the region between the antiferromagnetic phase and the ferromagnetic phase. At small doping, the spiral phase is unstable against phase separation due to its negative compressibility. When the Hund coupling is small, the system separates into spiral regions and antiferromagnetic regions. When the Hund coupling is large, the spiral phase disappears completely and the system separates into ferromagnetic regions and antiferromagnetic regions.