Directional ordering in the amorphous
Co75Si15B10
alloys by means of the magnetic after-effect (MAE) of the initial reluctivity and
its influence on the Perminvar effect have been investigated. Two peak MAE
spectra were obtained from isochronal measurements for as-cast as well as
annealed samples. The spectrum of the as-cast sample has peak maxima at 383
and 545 K. Comparing this MAE spectrum with the spectrum of amorphous
Co75B25
alloy, we identified the first peak as a result of Co–B atom pair reorientation
(B-type relaxation) and the second one at higher temperatures as a result
of Co–Si atom pair reorientation (Si-type relaxation). After annealing, the
peaks shift to 442 and 576 K, respectively. For the numerical analysis of
Co75Si15B10
MAE spectra we modified the micromagnetic model assuming the existence of more
relaxation processes, where each process is connected to the relaxation of one
metalloid element. The pre-exponential factor for B-type relaxation was found to be
τ0,AC(B) = 7 × 10−17 s with the most probable
activation energy QAC*(B) = 1.31 eV. These values correlate very well with the magnetic relaxation (MR) activation parameters of
Co75B25 alloy,
τ0,AC = 2 × 10−17 s
and QAC* = 1.35 eV. Si-type relaxation has activation parameters
τ0,AC(Si) = 6 × 10−18 s
and QAC*(Si) = 1.96 eV. After annealing the sample at 683 K for 30 min they change to values
τ0,AN(B) = 2 × 10−15 s,
QAN*(B) = 1.38 eV
and τ0,AN(Si) = 3 × 10−17 s, QAN*(Si) = 2.01 eV. The complicated shapes of the long-time isotherms reflect the superposition of two
relaxation processes. We have numerically split each isotherm into two sub-isotherms
representing the particular contributions of the two relaxation processes. The MAE
spectrum of the critical field measured on the as-cast sample also has two peaks, like the
reluctivity spectrum. The impact of Co–B and Co–Si atom pairs on the behaviour of the
domain wall stabilization potential is discussed for the explanation of the observed MR
results.