Melt-spun Pr2(Fe1−xCox)14B permanent magnet materials

Abstract

The substitution of cobalt for iron is known to increase the Curie temperature and stabilize the magnetic properties of melt-spun Nd2(Fe1−xCox)14B ribbons. The preparation of optimum permanent magnets from cobalt-substituted materials is, however, complicated by the need for nonstoichiometric starting materials which vary with the level of cobalt concentration. This paper contains the results of selecting compositions which optimize the room-temperature properties of melt-spun ribbons containing Pr2(Fe1−xCox)14B as the principal constituent. The hard magnetic properties of 11 cobalt concentrations were examined spanning the range x=0 to 1, inclusive. For cobalt concentrations up to x=0.5, the remanence and energy product did not change substantially from the x=0 values of 8 kG and 12 MGOe, respectively. Remanence and energy product decreased monotonically to their endpoint values of ∼5 kG and ∼5 MGOe for cobalt-rich alloys (x>0.5). The coercivity increased smoothly from 13 kOe for x=0 to 25 kOe for x=1. There was no evidence of the down turn in Hci normally associated with decreasing anisotropy.