Tuning of the magnetocaloric effect in La0.67Ca0.33MnO3-δ nanoparticles synthesized by sol-gel techniques

We report the effect of progressive reduction of the annealing temperature on the magnetocaloric effect (MCE) of La2/3Ca1/3MnO3-delta nanoparticles synthesized by the sol-gel technique. With this method, we are able to obtain particle diameters ranging form 60 to 500 nm. The peak in the MCE at the ferromagnetic to paramagnetic phase transition is strongly reduced as annealing temperature does, due to loss of the intrinsic first-order magnetic phase transition. This opens up a new way in which to tune the intrinsic properties of mixed-valence manganites, most of which are associated with the first-order character of the magnetic transition. (C) 2002 American Institute of Physics.