Phase Separation in Electronic Models for Manganites

TLDR

The study investigates the Kondo lattice Hamiltonian with ferromagnetic Hund’s coupling as a model for manganites and discusses experimental consequences of the identified phase‑separation regime. The authors analyze the classical limit of localized \(t_{2g}\) spins on 1‑, 2‑, 3‑, and infinite‑dimensional lattices using several numerical methods. The low‑temperature phase diagram shows phase separation between hole‑undoped antiferromagnetic and hole‑rich ferromagnetic regions, includes incommensurate spin correlations, and yields 3D critical temperature estimates that agree with experiment.

Abstract

The Kondo lattice Hamiltonian with ferromagnetic Hund's coupling as a model for manganites is investigated. The classical limit for the spin of the (localized) $t_{2g}$ electrons is analyzed on lattices of dimension 1,2,3 and $\infty$ using several numerical methods. The phase diagram at low temperature is presented. A regime is identified where phase separation occurs between hole undoped antiferromagnetic and hole-rich ferromagnetic regions. Experimental consequences of this novel regime are discussed. Regions of incommensurate spin correlations have also been found. Estimations of the critical temperature in 3D are compatible with experiments.