COERCIVITY ANALYSIS IN R17FE83-XBX MAGNETS

We studied the coercivity in magnets of composition R17Fe83-xBx (R = Nd, Pr and x = 8, 30), using measurements of the coercive field H(c), its angular dependence, and the magnetic viscosity coefficient S(v), for temperatures between 4.2 and 500 K. The results are discussed in relation to a model which does not specifically consider the detailed mechanisms involved in magnetization reversal, but which provides information about the magnetic properties in the activation volume v where magnetization reversal is initiated. It is concluded that the ordering temperature in v tends to be slightly smaller than in the bulk and that the room temperature anisotropy in v is not strongly reduced with respect to the bulk value. Finally, a direct evaluation of the dipolar interactions is in good agreement with results obtained from H(c)(T).