Spin-dependent magnetism and superparamagnetic contribution to the magnetocaloric effect of non-stoichiometric manganite nanoparticles

TL;DR

This study investigates the magnetic and structural properties of non-stoichiometric manganite nanoparticles, revealing spin-dependent magnetism and superparamagnetic effects that influence their magnetocaloric behavior.

Contribution

It provides new insights into the spin-dependent magnetism and superparamagnetic contributions affecting the magnetocaloric effect in manganite nanoparticles.

Findings

Reduction of Mn magnetic moment in paramagnetic phase

Critical behavior near second-order phase transition

Superparamagnetism influences magnetocaloric effect

Abstract

Despite extensive researches on manganites owing to widespread use in modern electronics, this class of metal oxides does not cease to surprise with its unique properties and new phenomena. Here we have studied structural and magnetic properties of non-Heisenberg manganite nanoparticles with a strong spin-electron coupling. During transition from low temperature ferromagnetic to high temperature paramagnetic state, the change in charge, valence and spin (magnetic moment) with the localization of eg-electrons on the manganese ions have been detected. With decrease in a temperature, the overstated effective magnetic moment of Mn ions in paramagnetic phase is reduced dramatically testifying to spin-dependent magnetism. The critical behavior of magnetization with determination of critical parameters near second-order phase transition has been studied comprehensively. Based on unusual behavior of temperature and field dependences of magnetic entropy change under different magnetic field, an additional influence of superparamagnetism of nanoparticles on the magnetocaloric effect has been found.