Effects of 3He Irradiation on the Anisotropy-Field Inhomogeneity and Coercive Force in Thin Permalloy Films

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Abstract
The effects of 3He irradiation on the inhomogeneity in the anisotropy‐field magnitude, Δ90, the angular dispersion, α90, and the coercive force, Hc, have been examined for vacuum‐deposited thin Premalloy films, with compositions ranging between 43% and 83% nickel. The changes induced in these parameters were developed at 60°C by exposing the films to 2 MeV 3He irradiation, in the presence of a 500 Oe orienting magnetic field applied parallel to the easy‐axis directions of the films. The total dosage received by the films was 2×1017 particles/cm2. As a result of this exposure, the values for both α90 and Δ90 decreased for all compositions, with the decrease a minimum in the vicinity of 78% nickel. Similarly, the coercive force decreased for most compositions, but was insensitive to irradiation for compositions around 81% nickel. Decreases in α90, Δ90, and Hc. were as much as 46% for some compositions; however, much of the decrease in Δ90 was primarily the result of an irradiation‐induced increase in the average uniaxial anisotropy field, Hk. On the basis of these results it was concluded that the irradiation induces an over‐all decrease in the internal strain in the film.