STUDY OF INFRARED DIVERGENCE FOR THE MAGNETIC-RELAXATION IN AMORPHOUS FE80B20 ALLOY

Using the two level model and unified theory of low frequency fluctuation, dissipation, and relaxation processes for condensed matter, the magnetic aftereffect spectrum has been calculated for the amorphous Fe80B20 alloy after annealing treatment for 4 h at 540 K. The calculated infrared divergence exponent n = 0.14, characteristic relaxation time tau-infinity = 2 x 10(-17) s and apparent activation energy E(A), at the temperature of the relaxation peak, is 1.7 eV. They are in good agreement with experiments (tau-infinity = 2.2 x 10(-17) s, E(A) = 1.66 eV, from Arrhenius plot, and E(A) = 1.87 eV, from the crystallization). The calculations support that for this amorphous alloy, the magnetic aftereffects are caused by the local rearrangement of the alignment of atom pairs Fe-B as a result of jumps of B atoms. Calculated energy E(A) increases as the temperature rises, indicating that the larger free volumes vanish faster than the smaller ones, as the temperature increases.