Intergrain interactions in nanocrystalline isotropic PrFeB-based magnets

An analysis of recoil loops measured during the demagnetization process has been carried out to obtain information about the nature of intergrain interactions in nanocrystalline isotropic PrFeB-based magnets. These interactions can be studied by plotting the deviations from the ideal value for the remanence given by the well-known Wohlfarth´s relation. Two kinds of interactions are mainly responsible for possible deviations: magnetostatic and exchange interactions. Here, a Pr_9.0Nd_3.0Dy_1.0Fe_72.0Co_8.0B_6.9Zr_0.1 alloy has been used to prepare a series of nanocomposites by intensive milling with various amounts of Fe. Coupling phenomena have been studied by analyzing the evolution of the δJ values when varying the 1) Fe-content; 2) annealing temperature, i.e., grain size; and 3) measurement temperature, i.e., variation of the exchange length.