Hyperfine field distributions of nanocrystalline alloys

Nanocrystalline alloys obtained by partial crystallization consist of nanocrystalline grains, i.e. a crystalline phase (CR) embedded in a disordered integranular phase. In the latter, the following structurally different atomic sites can be distinguished: (i) the amorphous residual phase (AM) which represents a remainder of original amorphous precursor depleted to atoms from which the respective crystallites are created, and (ii) the so-called interface zone (IF) assigned to atoms located on the surface of nanocrystals as well as in their immediate vicinity from the side of AM. The magnetic coupling between crystalline grains via intergranular phase, the suppression of the effective magnetic anisotropy and the decrease of the magnetostriction are sources of soft magnetic properties observed in nanocrystalline alloys. Classical magnetic measurements provide information about macroscopic magnetic properties (coercivity, magnetization, etc.). These measurements reflect simultaneously contributions both from the crystalline and the non-crystalline phases being present in the sample and in this respect, they cannot distinguish between them. On the other hand, Mossbauer spectroscopy provides information on all structurally different components separately, giving a possibility to study their magnetic and/or structural arrangements. Example material is Fe80-M7-Cu1-B12 (M=Mo,Nb,Ti.)