Temperature dependence of the anisotropy constants in Nd2Fe14B-based hard materials containing Dy

The authors have evaluated, at different temperatures, the second and fourth order anisotropy constants of Nd2Fe14B-based melt spun samples in which Nd was partly replaced by Dy. This was done through an analysis of the first quadrant demagnetization branches of the hysteresis loops in terms of a one sublattice coherent rotation model of non interacting isotropically distributed grains. The results evidence how the increase in Dy content corresponds both to the increase of the second order anisotropy constant and to a decrease of the fourth order one