A New Type of Magnetic Domain Structure in Negative Magnetostriction Ni-Fe Films

Ni-rich Ni-Fe and Ni evaporated polycrystalline films, the thickness of which is larger than a critical value, were found to be composed of stripe domains running parallel to the field previously applied to the films. B-H loops and magnetoresistance effect revealed that the magnetization in each domain points in one sense and deflects from the plane of the film upwards and downwards alternately. This type of domain structure is to be caused by the anisotropy whose easy axis is normal to the plane of the film, the origin of which is attributed to the magnetostrictive effect due to strains or defects in the film. The width of the domain increases with the thickness of the film, but does not depend sensitively on substrate temperatures and compositions. The critical thickness increases with an elevation of substrate temperatures and with decreasing Ni concentration. The stripe domain is no longer observable for the film containing Ni less than 80% where the magnetostriction constant is positive. The relation to the rotatable anisotropy is also discussed.