Magnetism and magnetocaloric effect in nanocrystalline La_0.67Ca_0.33Mn_0.9V_0.1O₃synthesized by nebulized spray pyrolysis

Abstract

Vanadium (V) substituted La(0.67)Ca(0.33)MnO(3) was synthesized in the nanocrystalline form using nebulized spray pyrolysis. Highly uniform nanoparticles of average size in the range 30-40 nm as revealed by transmission electron microscopic studies were prepared. Rietveld refinement of XRD patterns shows that the sample adopts an orthorhombic structure with the Pnma space group. The systematic change in lattice parameters and magnetic phase transition (T(C) = 252 K) as compared with those of nanocrystalline La(0.67)Ca(0.33)MnO(3) (TC = 260 K) indicate the substitutional effect of V. M-H curves in a certain temperature range reflect the superparamagnetic nature of the sample. The average particle size (similar to 28 nm) of the superparamagnetic clusters obtained from the Langevin fit is coincident with that of the nanocrystalline clusters revealed by the high-resolution transmission electron microscopy images. The Arrott plots reveal the first order character of magnetic phase transition of the sample. The peak magnetic entropy change (Delta S(max)) of these nanopowders is estimated to be about 4.5 J kg(-1) K(-1) for a magnetic field of 5 T at 252 K. Compared with the bulk La(0.67)Ca(0.33)Mn(0.9)V(0.1)O(3), the entropy change of the nanoparticles is found to be smaller, but the entropy change occurs over a broad temperature range, giving rise to a large relative cooling power.