Size and anisotropy effects on magnetic properties of antiferromagnetic nanoparticles

Based on the Heisenberg model taking into account single-ion anisotropy and using a Green's function technique we have studied the influence of size and anisotropy effects on magnetization M  , Neel temperature TNTN, coercive field HcHc and spin excitation energy of antiferromagnetic nanoparticles. The properties are compared with those of ferromagnetic nanoparticles. We have shown that the enhanced magnetization M   and coercive field HcHc of antiferromagnetic nanoparticles is a surface effect, which is due to uncompensated surface spins. Moreover, the shape of the coercive field curve can be significantly influenced by surface magnetic anisotropy.