Synthesis and magnetocaloric properties of La0.7Ca0.3MnO3 nanoparticles with different sizes

La0.7Ca0.3MnO3 nanoparticles with different average sizes were prepared via a polyacrylamide gel route, where the particle size was tailored by using different chelating agents. The samples prepared by using the chelating agents acetic acid (S1), oxalic acid (S2), citric acid (S3) and EDTA (S4) have an average particle size of 30, 37, 45 and 50 nm, respectively. The as-prepared particles are regularly shaped like spheres. Magnetocaloric properties of samples S1 and S4 that respectively have the smallest and largest particle size were systematically investigated. The paramagnetic–ferromagnetic transition temperature TC is observed to be 260 K for sample S1 and 267 K for sample S4. The nature of the magnetic phase transition at TC is determined to be second order. The magnetic entropy change is found to be extended over a wide range of temperature around TC, and its maximum value at an applied magnetic field of 15 kOe is obtained to be 1.01 and 1.20 J kg−1 K−1 for samples S1 and S4, respectively.

► La0.7Ca0.3MnO3 nanoparticles with different sizes were prepared via a polyacrylamide gel route.
► Samples with average size of 30–50 nm were obtained by using different chelating agents.
► Magnetocaloric properties of the samples were investigated.