Ichiro Morimoto

M-Induced Anisotropy in Electrodeposited Polycrystalline Permalloy Films

M-induced uniaxial anisotropy, Ku, is investigated for electrodeposited polycrystalline permalloy films in a range from 40 to 100% Ni. The observed Ku is composed of two terms which are respectively sensitive and insensitive to annealing treatment below 200°C. These terms correspond to the terms due to magnetostrictively induced anisotropic strain and directional ordering of iron pairs, respectively. The latter separated from the observed Ku by annealing below 200°C is in good agreement with the data obtained for bulk permalloy. The observed Ku can be quantitatively fitted to the sum of the former deduced theoretically and the latter obtained experimentally except for near 100% Ni films, if inhomogeneous composition of film along the thickness is evaluated. In a case of near 100% Ni, the values of Ku are considerably smaller than that deduced from the theoretical model. This may be related to the high angular dispersion of easy axes of the films.

Annealing Behavior of Induced Anisotropy in Electrodeposited Polycrystalline Nickel Films

The annealing behavior of electrodeposited nickel films, that is, the annealing decay of the magnetostrictively induced uniaxial anisotropy was investigated after deposition and after stabilization at 70°C when the films were annealed isothermally in a magnetic field parallel to the magnetic hard axis. The fractional anisotropy of P =( K u ( t )- K u (∞))/( K u (0)- K u (∞)) can be expressed as a function of annealing time t in a form of P =exp (- t /τ) 1/3 in all as-deposited and stabilized films, where τ is a relaxation time. Such one-third power dependence can be well explained by such a model that defects annihilate into grain boundaries, and this model also explains a stabilizing effect. The activation energy of 1.1 5 eV for the stabilized films is in good agreement with that of stage III due to interstitial atoms in bulk nickel data. In a case of as-deposited films the lowering of the activation energy to 0.7 4 eV may partially depend on an annihilation of divacancies.