Effective magnetic moment of magnetic multicore nanoparticles

We carry out Monte Carlo simulations to study the effective magnetic moment mu(eff) in the low-field region of magnetic multicore nanoparticles. Transmission electron microscopy and scanning electron microscopy images show that these particles contain a number of magnetic nanocrystals (MNCs) randomly packed in a single cluster of total volume V-tot. We illustrate how the initial magnetic susceptibility chi(0) of magnetic multicore nanoparticles can be straightforward derived from mu(eff) computed at zero magnetic field. We observe that dipolar interactions between MNCs and polydispersity of the MNCs contribute to increase and to decrease mu(eff)/V-tot, respectively, while magnetic anisotropy of the MNCs does not show any effect. In all three cases, mu(eff)/V-tot can be described by a linear relation to (mu B/k(B)T)(2) that we analytically derived for low applied fields.