Temperature dependence of coercivity and magnetic relaxation in a Mn–Al–C permanent magnet

The kinetics of magnetization reversal in a rare-earth-free Mn-Al-C permanent magnet is reported. The L10-phase material was prepared using a combination of the melt spinning and spark plasma sintering techniques and characterized with a vibrating sample magnetometer. Magnetic relaxation and susceptibility experiments were performed. Magnetic viscosity, fluctuation field and activation volume were measured in a wide temperature range. These data were used to analyze the magnetization reversal and temperature dependence of the coercive field. The thermally activated mechanism of the reversed nucleus formation was confirmed for the intermediate temperatures. The role of wall thickness and crystallite size as additional characteristic lengths in magnetic domain nucleation is discussed.