Hopping mechanism and Griffiths singularity in La0.7Ca0.25Sr0.05MnO3/Mn3O4 composite nanoparticles

Abstract

This study investigates the electronic and magnetic properties of La0.7Ca0.25Sr0.05MnO3/Mn3O4 composite nanoparticles, focusing on the interplay between charge transport mechanisms and magnetic fluctuations. The composite nanoparticles exhibit a transition from paramagnetic to ferromagnetic behavior with Curie temperatures (TC) of 276.2, 272.2, and 274.2 K for particle sizes of 28, 30, and 32 nm, respectively. Electrical resistivity measurements indicate that hopping conduction dominates electron transport, with variable-range hopping (VRH) providing a more accurate description of the conduction mechanism than the Arrhenius nearest-neighbor hopping model. The nanoscale magnetic clusters induced by the Griffiths phase persist above TC, introducing magnetic fluctuations that deviate from the classical Curie–Weiss law. These fluctuations significantly influence both the magnetization and transport properties by creating magnetic inhomogeneity and enhancing charge localization. The coupling between the Griffiths phase and VRH conduction suggests that these materials could have potential for applications in areas such as spintronics and other electronic technologies.