Effect of nanocrystalline structure on magnetocaloric effect in manganite composites (1/3)La0.7Ca0.3MnO3/(2/3)La0.8Sr0.2MnO3

Poly- and nanocrystalline manganite composites (1/3)La0.7Ca0.3MnO3 and /
(2/3)La0.8Sr0.2MnO3 prepared by the sol-gel method are studied by magnetic and transport
measurements. The Arrott plots and universal curve of magnetic entropy change confirm that
magnetic transition is of the second order. The magnetocaloric effect of polycrystalline
composite is found to be roughly twice smaller as compared to the polycrystalline Ca- and Srbased
parent phases. The nanocrystalline composite of the same composition exhibits only 8
% reduction of magnetic entropy change. Due to the large temperature spread of
magnetocaloric effect the relative cooling power RCP of nanocrystalline composite is about
three times larger as compared to the nanocrystalline Ca- and Sr- based parent phases. The
maximum magnetic entropy change DSMAX and relative cooling power RCP are found to be
more sensitive to magnetic field strength for the nano- than for polycrystalline composites
studied.