Directional ordering in amorphous Co Si B alloys
Abstract
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 tgr0,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, tgr0,AC = 2 × 10-17 s and QAC* = 1.35 eV. Si-type relaxation has activation parameters tgr0,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 tgr0,AN(B) = 2 × 10-15 s, QAN*(B) = 1.38 eV and tgr0,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.
- Publication:
-
Journal of Physics Condensed Matter
- Pub Date:
- June 2004
- DOI:
- 10.1088/0953-8984/16/21/023
- Bibcode:
- 2004JPCM...16.3745A