Insulator-metal transition shift related to magnetic polarons in La 0.67- xY xCa 0.33MnO 3

Abstract

The magnetic transport properties have been measured for La 0.67-x Y x Ca 0.33 MnO 3 (0 ≤ x ≤ 0.14) system. It was found that the transition temperature T p almost linearly moves to higher temperature as H increases. Electron spin resonance confirms that above T p , there exist ferromagnetic clusters. From the magnetic polaron point of view, the shift of T p vs. H was understood, and it was estimated that the size of the magnetic polaron is of 9.7~15.4 Å which is consistent with the magnetic correlation length revealed by the small-angle neutron-scattering technique. The transport properties at temperatures higher than T p conform to the variable-range hopping mechanism.

Evidence and evolution of magnetic polaron in HgCr2Se4 investigated by electron spin resonance

“…Above T min , the small MPs are regarded as islands with long distance between each other and hop to nearest neighbor by thermal activation [31,41]. ΔH pp is suppressed with decreasing temperature induced by motional narrowing effect.…”