Fluctuations of the saturation magnetostriction constant in amorphous ferromagnets

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Abstract
Fluctuations of the magnetostriction constant lambda with correlation length larger than the correlation length of the magnetic moments, affect the anisotropy field introduced by applying external stress. The experimental anisotropy field contains two terms. The first one is the anisotropy field corresponding to the average lambda . The second term is a series in increasing powers of the stress. The coefficient of the nth power encloses the nth moment of the lambda distribution. When the experimental value of lambda is determined by means of magnetoelastic effects, it is obtained from the stress derivate of the magnetoelastic anisotropy field. Sinc the existence of fluctuations leads to a series of powers of the stress, the experimental lambda would also depend on the stress. This dependence is expected to be enhanced when the average lambda vanishes. It is suggested that the stress dependence of lambda observed in nearly zero magnetostriction, Co-rich alloys could be related to fluctuations in lambda .