Insulator-metal transition shift related to magnetic polarons in La0.67-xYxCa0.33MnO3

TL;DR

This study investigates how magnetic polarons influence the insulator-metal transition in La0.67-xYxCa0.33MnO3, revealing a linear shift of transition temperature with magnetic field and characterizing magnetic polaron sizes.

Contribution

It provides new insights into the role of magnetic polarons in transition shifts and estimates their size using ESR and neutron scattering data.

Findings

Transition temperature Tp increases linearly with magnetic field H.

Magnetic polarons have a size of approximately 9.7 to 15.4 angstroms.

Transport above Tp follows variable-range hopping mechanism.

Abstract

The magnetic transport properties have been measured for La0.67-xYxCa0.33MnO3 (0 <= x <= 0.14) system. It was found that the transition temperature Tp almost linearly moves to higher temperature as H increases. Electron spin resonance confirms that above Tp, there exist ferromagnetic clusters. From the magnetic polaron point of view, the shift of Tp vs. H was understood, and it was estimated that the size of the magnetic polaron is of 9.7~15.4 angstrom which is consistent with the magnetic correlation length revealed by the small-angle neutron-scattering technique. The transport properties at temperatures higher than Tp conform to the variable-range hopping mechanism.