Magnetic properties of granular ferromagnetics

Experiments demonstrate that the magnetization of Fe-x(SiO2)(1-x)-nanocompo site at magnetic fields H less than or equal to 20 T depends rather weakly on temperature T = 4-300K. Thus, the Langevin model for the magnetization i s invalid. We explain our results in the frame of a simple model taking int o account distributions of non-spherical granules' orientations and forms. Calculated field dependence of the magnetization agrees with the experiment everywhere except for the fields H similar to 10 kOe, where calculated val ues are somewhat higher (up to similar to 20%) than experimental ones. Thes e discrepancies are related to the magnetic "glass" behavior of the magneti zation. (C) 2001 Elsevier Science B.V. All rights reserved.