Magnetic methods of structural analysis of nanocrystalline alloys : magnetic granulometry

Non-conventional, two phase granural magnetic composed of magnetic crystallites embedded in amorphous matrix, magnetic as well, are presently widely applicable in electronics owing to thier exstremely good magnetic softness. They are produced by devitrification of rapidly quenched metalic glasses performed onder well controlled annealing conditions. Besides of the practical importance, these granural magnets also become excellent objects for the basic research on magnetism. Depending on the composition of the parent material, size and vilume content of the crystallites and also on the temperature of measurments, they show a variety of magnetic phases. Additionally, because if the nanometr size of the crystallites, their usrface to volume ratio is very large allowing to expect nivel properties not occuring in the bulk magnetic materials (magnetic atoms on the surface reveal different symmetry than those in the bulk). To study the mentioned magnetic phenomena, granular structure of nanocrystalline magnets must be known (size of the crystallites and its distribution, their volume content as well as the composition). All these parameters can be calculated applying magnetic methods if only the sttudied material fulfils the conditions at which the superparamagnetic behaviour of the crystallites can occur. The procedures applied to calculate structural parameters will be exemplified using granular magnet comprising of Fe(Si) nanocrystallites embedded in the residual amorphous matrix of the initially FeCrCuNbSiB metallic glass. The results obtained this way will be compared with those given by conventional methods (TEM and X-ray diffraction).