Anomalous spin susceptibility and magnetic polaron formation in the double exchange systems

TL;DR

This study investigates the magnetic susceptibility and spin correlations in double-exchange systems, revealing local ferromagnetic clusters and magnetic polaron formation near the transition temperature, consistent with experimental observations.

Contribution

It provides a Monte Carlo analysis of spin behavior in doped manganites, highlighting local cluster formation and magnetic polarons in the double-exchange model.

Findings

Deviations from Curie-Weiss behavior near T_c

Formation of ferromagnetic clusters of 3-4 lattice spacings

Evidence for magnetic polaron formation

Abstract

The magnetic susceptibility and spin-spin correlation of the double-exchange model for doped manganites are investigated through the Monte Carlo calculations on the three-dimensional lattice model. Deviations of the susceptibility from the Curie-Weiss behavior above the ferromagnetic ordering temperature $T_c$ seem to indicate a formation of local ferromagnetic clusters in the vicinity of $T_c$, which is consistent with recent electron paramagnetic resonance experiments for La$_{2/3}$Ca$_{1/3}$MnO$_3$. A further analysis of the spin-spin correlations show the ferromagnetic cluster size to be three-to-four lattice spacings, suggesting that the charge carriers may form magnetic polarons.