Analysis of the activation energy spectra of the induced anisotropy in amorphous Co58Ni10Fe5Si11B16

Magnetic annealing kinetics for the induced anisotropy and the coercive field in amorphous alloys Co58Ni10Fe5Si11B16were studied. Spectra of activation energies for "reversible" and "irreversible" annealing processes are determined and discussed in the light of a micromagnetic theory of the induced anisotropy recently proposed [1] on the basis of the thermodynamics of two-level systems [2] : 1. The formation of induced anisotropies in Co58- Ni10Fe5Si11B16is attributed to an atom pair ordering process around free volumes. 2. "Reversible" annealing processes are characterized by a spectrum of activation energies ranging from 1.8 eV to 2.3 eV. The small pre-exponential factor of τo,R = 6.10^-16s points to a localized atomic, thermally activated process. 3. "Irreversible" annealing processes are characterized by small activation energies ranging from 0.5 eV to 1.0 eV. The large pre-exponential factor τo, A = 3-10^-4s points to a long-range migration of free volumes leading to an immobilization of atom pairs.