Ultra low frequency Barkhausen noise versus domain structure and reversal magnetization in sintered (NdDy)(FeCo)B magnets

The continuous and jumpwise components of the magnetic relaxation were analyzed in the (NdDy)(FeCo)B sintered magnets in the stationary magnetic field close to the coercive field. The jumpwise magnetic relaxation of the extremely low frequency (similar to 0.01-0.1 Hz) and a large average amplitude (similar to 0.2%) of the saturation magnetization were revealed. The 2%-3% Sm doping ions increase the continuous relaxation up to 2 times and decrease the magnetization probability and average jump size down to 1.5 times. The spectral power of the magnetization jumps corresponds to the white noise appearing due to the uncorrelated individual magnetization reversal of the similar to 10(3) independent grains. The continuous relaxation is due to the domain wall motion. Magnetic force microscopy allows us to distinguish the domain walls shift and the reversal of the grains to estimate the energy and width of the domain walls. First order reversal curve analysis revealed the contribution of the 2-14-1 phase and isolated 1-4-1 phase inclusions and the effect of Sm doping on the distribution of the switching and interaction fields of these phases. Published by AIP Publishing.