  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.
