Dependence of the Properties of Magnetic Nanoparticles on the Interparticle Separation

Dependence of the magnetic properties of FePt nanoparticles with an average diameter, D, of 5 nm on the interparticle separation, d, has been investigated by employing different spacer molecules. The observed decrease in the blocking temperature and Curie-Weiss temperature with increase in d as well as the increase in saturation magnetization with increase in d have been explained on the basis of a simple model for the case d << D where the magnetic nanoparticles are treated as finite dipoles coupled through anisotropic multipolar interactions.