Origin of the anomalous size dependent blocking temperature of nanoparticles

Analysis of available experimental data reveals that monodisperse Mn3O4 nanoparticles show anomalous size dependent blocking temperature. This work presents a simple analysis which provides insight into the nature of this anomaly. My analysis pointed out that the magnetic anisotropy K mag follows the power law K mag ∼ D − 3 in all Mn3O4 nanoparticles ( D is the average diameter of particles). The influences of the size dependent magnetic anisotropy of Mn3O4 nanoparticles on the size dependent blocking temperature, the coercivity of Mn3O4 nanoparticles, and also the magnetic properties of core-shell MnO/Mn3O4 nanoparticles were analyzed.