'Exchange spring' behavior in nanocomposite hard magnetic materials

The magnetic properties of nanocrystalline melt-spun single-phase (Nd2Fe14B-type) and composite (Nd2Fe14B + alpha-Fe or Nd2Fe14B + Fe3B + alpha-Fe) magnets have been studied systematically in an attempt to understand better their 'exchange spring' behavior. The reversibility of the recoil demagnetization curves has been found to increase with increasing content of the soft phase giving rise to the characteristic exchange spring behavior only in nanocomposite samples. delta M plots indicate positive interactions of the exchange type for small fields; for fields higher than the remanence coercivity, magnetostatic interactions become dominant. The relative strength of the magnetostatic interactions is increased in samples with higher soft phase contents.