Critical phenomena of magnetization, magnetocaloric effect, and superparamagnetism in nanoparticles of non-stoichiometric manganite

Magnetic nanoparticles of the La0.6Ag0.2Mn1.2O3 manganite with superstoichiometric manganese have been obtained using nitrate pyrolysis method. Structure, phase composition, morphology, and size of the nanoparticles have been determined. Magnetic properties of the La0.6Ag0.2Mn1.2O3 nanoparticles have been studied near the temperature of their magnetic ordering. It has been shown that magnetization near critical temperature is equilibrium and superparamagnetic. It has been found that magnetization and a change in entropy have critical behavior with a large value of the magnetocaloric effect. Interrelation between the critical indices of magnetization and the magnetocaloric effect has been established. In strong magnetic field, these properties of the nanoparticles have behaviour comparable with bulk samples. In weak magnetic field, the effect of superparamagnetism on the entropy has been found. The magnitude of the contribution from superparamagnetism to the magnetocaloric effect has anomalous temperature dependence. The obtained results of the influence of superparamagnetism on the thermomagnetic properties of the nanoparticles near critical temperature are important to understand and can be used for applied applications. (C) 2020 Elsevier B.V. All rights reserved.