ALTERNATING-CURRENT SUSCEPTIBILITY STUDY OF A 2-PHASE NANOCOMPOSITE FE88ND6B6 ALLOY IN THE TEMPERATURE-RANGE 77-990 K

Alternating current-initial susceptibility studies on as-spun amorphou s and rapid-thermal-annealed two-phase nanocomposite Fe88Nd6B6 alloy r ibbons are performed at 77-990 K. A novel means of quantitatively esti mating the amount of the residual amorphous phase in heated ribbons is also derived from the chi(ac) measurement. Experimental results indic ate that the amount of the residual amorphous phase decreases with an increasing heating temperature. The residual amount is 28.87 vol% afte r the amorphous ribbons are heated to 773 K, and then becomes undetect able when the temperature reaches heating to 923 K. The amount of the residual amorphous phase can be described as follows: R (in vol %)=0.8 57T/(T-753)-4.392, where T denotes the heating temperature above 753 K . In addition, the full width at half-maximum of the chi(ac) peak corr esponding to the Curie temperature of the Nd2Fe14B phase correlates we ll with the extent of exchange coupling interaction between the hard a nd soft nanophases. Furthermore, the spin reorientation transition tem perature of the Nd2Fe14B nanophase in the two-phase nanocomposite Fe88 Nd6B6 alloy shifts to 110 K, i.e., significantly lower than 135 K for the Nd2Fe14B single crystal. This shift is attributed to the exchange coupling effect between the nanophases. (C) 1998 American Institute of Physics. [S0021-8979(98)05007-5].