Magnetic phase transitions and magnetic anisotropy in Nd 2Fe 14 − xCo xB compounds

Abstract

The temperature dependence of the anisotropy field of Nd 2Fe 14 − x -Co x B has been measured between 77 K and the Curie temperature, using the singular point detection (SPD) technique. The anisotropy field at room temperature is found to decrease with increasing cobalt content. Measurements of the temperature dependence of the initial susceptibility show that at a temperature T 1, which is below room temperature, the easy magnetization direction changes. The origin of the change is attributed to the neodymium-sublattice anisotropy. For the cobalt-rich samples ( x ⩾ 5) it is found that at temperatures T 2 higher than ambient temperatures a second spin reorientation takes place, which is attributed to the competing effect of the neodymium sublattice anisotropy and the 3d sublattice anisotropy.