Size effects and interactions in La0.7Ca0.3MnO3 nanoparticles

La_0.7Ca_0.3MnO₃ (LCMO) nanoparticles with average diameter of 16-73 nm were prepared by reactive milling and thermal processing methods. Interaction and size effects on the magnetic properties of the LCMO nanoparticle samples were investigated. Phenomena related to the interparticle interaction, such as an un-overlapping of the M(H_ext,T)/M_S vs. H_ext/T scaling plots and a Curie-Weiss rather than Curie law behavior of the dc susceptibility at high temperatures were analyzed. The magnetization curves of interacting nanoparticles were well described by using the mean-field approximation. The dependence of the blocking temperature T_B on the strength of the interactions, magnetic anisotropy, as well as the thermal dependence of magnetization deviates from the expected Bloch law was also estimated.