Structural magnetic relaxation of amorphous Co75B25 alloy

Abstract The structural magnetic relaxation of the amorphous Co75B25 alloy in the as-cast and annealed states has been investigated by means of the magnetic after-effect (MAE) spectroscopy. The relaxation process is realised by reorientations of atom pairs minimizing a free energy of the ferromagnetic system. The pre-exponential factor τ0 = 2 × 10−17 s and the most probable activation energy Q* = 1.34 eV have been obtained from numerical analyses of MAE spectra and isotherms of the amorphous alloy in the as-cast state. A peak of the 180 s isochrone occurs at the temperature 383 K. Annealing at 653 K for 1800 s reduces relaxation intensity Δr/r from 38% to 9% and shifts the peak temperature to 473 K. Activation parameters of the magnetic relaxation of the annealed Co75B25 alloy were changed to τ0 = 9 × 10−16 s and Q** = 1.53 eV. These effects are connected with reduction of the free volumes near to active atom pairs. Numeric analyses of the MAE isochrones and long time isotherms give very similar activation energy spectra.