Dependence of the coercive force on the magnetic field sweep rate in (PrDy)(FeCo)B alloys

The dependence between the coercive force and the average hysteresis loop record time was revealed in sintered (Pr$_{1-x}$Dy$_{x}$)$_{13}$(Fe$_{1-y}$Co$_{y}$)$_{79}$B$_{8}$ magnets. The coercive force was established to grow by 22% with an increase in the average hysteresis loop sweep rate within a range of 1.1 $\times$ 10$^{2}$–3 $\times$ 10$^{5}$ Oe/min, obeying a logarithmic dependence on the loop passage velocity with saturation at low rates. Some domain structure transformations produced by a magnetic field in the process of magnetization were established by magnetic force microscopy.