Study of Percolative Transitions with First-Order Characteristics in the Context of CMR Manganites

TL;DR

This paper presents a semi-phenomenological model for manganites that captures abrupt, first-order percolative transitions caused by phase competition and correlations, aligning with experimental observations of their magneto-transport properties.

Contribution

It introduces a new model that explains first-order percolative transitions in manganites, differing from standard percolation theories, based on coexisting clusters with smooth surfaces.

Findings

The model reproduces abrupt percolative transitions observed experimentally.

It suggests phase competition triggers a new class of percolative processes.

Transitions can be driven by magnetic field-induced alignment of ferromagnetic clusters.

Abstract

The unusual magneto-transport properties of manganites are widely believed to be caused by mixed-phase tendencies and concomitant percolative processes. However, dramatic deviations from "standard" percolation have been unveiled experimentally. Here, a semi-phenomenological description of Mn oxides is proposed based on coexisting clusters with smooth surfaces, as suggested by Monte Carlo simulations of realistic models for manganites, also briefly discussed here. The present approach produces fairly abrupt percolative transitions and even first-order discontinuities, in agreement with experiments. These transitions may describe the percolation that occurs after magnetic fields align the randomly oriented ferromagnetic clusters believed to exist above the Curie temperature in Mn oxides. In this respect, part of the manganite phenomenology could belong to a new class of percolative processes triggered by phase competition and correlations.