Fine "mist" vs large droplets in phase separated manganites

Abstract

The properties of phase-separated systems, e.g. manganites, close to a I order phase transition between charge-ordered insulator and ferromagnetic metal, are usually described by the percolation picture. We argue that the correlated occupation of metallic sites leads to the preferential formation of larger metallic clusters, which explains the often observed inverse, or ``overshot'' hysteresis in manganites (when the resistivity with increasing temperature is larger than with decreasing T). It also explains the recently discovered thermal cycling effect in manganites. Thus in treating this and similar systems in percolation picture, not only the total concentration of metallic phase, but also the distribution of metallic clusters by shape and size may significantly influence the properties of such systems.