Phase Separation in Models for Manganites

Abstract

Using computational techniques the phase diagram of models for manganites is studied. In the absence of Jahn–Teller phonons three regimes are found to dominate the low temperature properties of these models: (i) a ferromagnetic region induced by the double-exchange mechanism; (ii) a region with incommensurate spin correlations at small Hund coupling; and (iii) a novel regime of phase separation (PS) between hole-rich ferromagnetic and hole-poor antiferromagnetic domains. PS occurs both at high- and low density of eg electrons. Experiments for manganites compatible with the presence of PS are discussed. In the presence of dynamical Jahn–Teller phonons, PS is also observed and, in addition, staggered orbital order exists in some regions of parameter space.