07-19U

For three-dimensional model of noninteracting magnetic nanoparticles effects of random orientation of magnetic anisotropy axes and polydispersity in size of particles on thermodynamic properties of the system are considered. Comparison with results obtained for classical Stoner-Wohlfarth model is performed. It is shown that the maximum observed in temperature dependence of magnetization becomes more smear when randomness in orientation and/or size distribution increases. In the case of homogeneous distribution in orientation of anisotropy axes the superparamagnetic behaviour is observed.