The saturation magnetostriction of thin polycrystalline films of iron, cobalt, and nickel

Abstract

The saturationmagnetostriction λ s of Fe, Co, and Nifilms was measured by the cantilevered substrate technique. The values of λ s , −6.8×10−6 and −38×10−6, obtained for Fe and Ni, respectively, are in accord with bulk published values. A unique value of λ s could not be obtained for Co because the sputtered or evaporated Co films were admixtures of face‐centered‐cubic and hexagonal close packed phases and the magnitude and sign of λ varied with the fcc content. Increasing the substrate temperatures during film deposition decreases the fcc content; however, this also caused the development of a C‐axis hexagonal texture normal to the film plane. Annealing the films at ∼500 °C caused a similar but more pronounced texture. Then, because of the uniaxial anisotropy of Co, the films could not be magnetically saturated and the magnetostrictive behavior changed; i.e., the transverse and longitudinal λ were both negative and in some instances the transverse λ was larger than the longitudinal λ.