Physics of nanocrystalline magnetic materials

The mechanism of exchange coupling will be discussed in single phase hard magnetic materials as well as in nanocomposites. Temperature dependent anisotropy field H-A measurements will be presented on Pr-Fe-B samples. Additionally the temperature dependence (4.2K < T < 300K) of the saturation magnetisation, of the remanence and of the coercivity will be presented. From the ratio J(r/)J(S) the degree of enhancement can be deduced. At lower temperatures a decoupling of the grains was observed which becomes also visible in the H-A(T) behaviour. The influence of the exchange coupling on the Curie temperatures as well as on the spin reorientation temperature for Nd-Fe-B and Pr-Fe-B based samples is shown.