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Magnetic nanoparticles of the La 0. 6 Ag 0. 2 Mn 1. 2 O 3 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 La 0. 6 Ag 0. 2 Mn 1. 2 O 3 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. • Magnetically homogeneous La 0 · 6 Ag 0 · 2 Mn 1 · 2 O 3 nanopowder has been prepared. • It has been found that the soft magnetic nanoparticles are in SPM state near T C. • Critical indices obtained experimentally are in good agreement with each other. • In small H , an entropy change Δ S M associated with SPM near T C has anomalous maximum. • High values of Δ S M in the nanopowder under small magnetic field have been obtained. [ABSTRACT FROM AUTHOR]