Tunable magnetocaloric effect in La0.7Ca0.3MnO3 nanoparticles

Abstract

We study ferromagnetic to paramagnetic transition using Banerjee criterion in colossal magnetoresistive La[Formula: see text]Ca[Formula: see text]MnO3 nanoparticles of different sizes (20, 26 and 32 nm). These particles are chemically prepared by a modified citrate route. Particle sizes are estimated by X-ray diffraction (XRD). Sample morphology and size distribution are examined by a transmission electron microscope. Order of transition is determined by measuring magnetic field dependence of magnetization near Curie temperature T[Formula: see text]. Our results reveal second-order magnetic transition in all three different-sized particles in contrast to the first-order transition reported in bulk samples. This is further supported by temperature dependences of zero-field-cooled (ZFC) and field-cooled (FC) magnetizations. FC curves show gradual transition for all three samples without any saturation region as is the case of bulk. T[Formula: see text] is extracted from ZFC curves and is found to be 240 K for 20 nm particles and 258 K for both 26 and 32 nm particles. Magnetocaloric effect as a function of particle size also confirms the second-order magnetic transition in all three samples. The relative cooling power at 20 kOe is found to be decreasing with decreasing particle size.