The magnetization reversal has been examined by the temperature dependence of the coercivity, the initial magnetization curve, minor hysteresis loops, and thermal activation in isotropic nanocrystalline Pr-Fe-B ribbons. The coercivity mechanism is found to vary with temperature. At 20 K, the coercivity is mainly determined by strong pinning (by random inhomogeneities); while at room temperature it is mainly controlled by the nucleation of domain and localized pinning at grain boundaries. The influence of the grain-boundary character on magnetic hardening and the temperature dependence of intergrain exchange coupling and anisotropy have been investigated to discuss the coercivity mechanism.

• Received 31 May 2002

DOI:https://doi.org/10.1103/PhysRevB.66.184436