Magnetic properties and magnetocaloric effect of LaMnO3 nanoparticles prepared by using the sol-gel method

摘要

We synthesized LaMnO3 nanoparticles (NPs) with an average particle size of similar to 25 nm by using a sol-gel method with polyvinyl alcohol (PVA). X-ray diffraction studies revealed that the samples exhibited a rhombohedral single phase. The Curie temperature (T (C)) of the ferromagneticparamagnetic (FM-PM) phase transition increased from 218 K for PVA = 0 ml to 287 K for PVA = 5 ml. Concurrently, the magnetic properties of the sample prepared with PVA were improved remarkably. This was ascribed to the presence of excess oxygen which increased the Mn4+/Mn3+ ratio and the FM interactions in the NPs. Particularly, we found that the samples underwent a second-order magnetic phase transition at the T (C). At H = 10 kOe, although their maximum magnetic-entropy change (Delta S (m) ) was small, 0.2 similar to 0.3 J/kg K, the linewidths of the |Delta S (m) (T)| curves were remarkably large, 50 similar to 70 K, leading to a quite large relative cooling power of similar to 17 J/kg.