HYSTERESIS BEHAVIOR AND MICROSTRUCTURE OF EXCHANGE-COUPLED R(2)FE(14)B(1) ALPHA-FE MAGNETS/

The hysteresis behavior of nanocomposite R(2)Fe(14)B/alpha-Fe magnets with R = Nd and Pr was investigated at low temperatures. The room temp erature coercivity depends on annealing with a peak value at 700 degre es C. The low coercivity of samples annealed at temperatures below the optimum is due to incomplete transformation of R(3)Fe(62)B(14) to R(2 )Fe(14)B phase. Hysteresis loops of Pr2Fe14B/alpha-Fe samples change f rom a smooth to a constricted loop when temperature is varied from 300 to 10 K. This may be due to the decoupling of a fraction of the large r 2:14:1 grains which reverse independently of the rest of the sample.