Magnetization reversal of Nd-Fe-B sintered magnets at low temperatures

Barkhausen-like magnetization jumps at temperatures T < 9.5 K and the behaviour of the coercive field at low temperatures are studied in sintered Nd-Fe-B magnets with different chemical and phase compositions. The nonlinear temperature dependence of the coercive field H c is well described in the thermal activation model at T > 10 K. The low temperature anomalies of H c are discussed in terms of the quantum tunneling of the domain wall through the intergrain boundaries.