ИСТИНА

Experiments on the impact of the size of magnetite clusters on various magnetic properties (magnetic moment, Curie temperature, blocking temperature etc) have been carried out. The changes of the size of nanoparticles (NPs) cause a shift in the Curie temperature and changes in the specific magnetic properties of the iron NPs. The experimental data is interpreted on the basis of Monte Carlo simulations for the classical Heisenberg model with different bulk and surface magnetic moments. It is demonstrated experimentally and by theoretical modeling that the magnetic properties of magnetite NPs are determined not only by their sizes, but also by their surface spin states, while both growing and falling dependences of the magnetic moment (per Fe 3O 4 formula unit) are possible, depending on the number of magnetic atoms in the nanoparticle.