Disordered magnetism at the grain boundary of pure nanocrystalline iron

The low-temperature magnetic behavior of ball-milled nanocrystalline Fe is reported. The results of de and ac susceptibility, remanence, and magnetic relaxation measurements indicate a transition from a high-temperature ferro magnetic state to a low-temperature disordered regime, where a collective f reezing of the crystallites magnetic moments occurs. It is proposed that th e behavior is determined by the presence of the structurally disordered gra in boundaries, showing spin-glass-like properties.