Study of magnetic nanowires of amorphous Co$_{20}$Fe$_{60}$B$_{20}$ prepared by oblique angle deposition on nanorippled substrate

Abstract

An array of magnetic nanowires of amorphous Co$_{20}$Fe$_{60}$B$_{20}$ alloy has been prepared by oblique angle deposition of material on nanorippled substrate. The angle of incidence is chosen such that the deposition takes place on only one facet of the nanoripples. Grazing incidence small angle x-ray scattering measurement has been done in order to characterize the morphology of the nanowires. It is found that the oblique angle deposition results in columnar growth, and each individual nanowire consists of nanocolumns having average diameter of 7 nm and a tilt angle of 37° with respect to the surface normal. Azimuthal angle dependence of longitudinal magneto-optical Kerr effect measurement shows that the nanowires possess a well-defined uniaxial magnetic anisotropy with the easy axis of magnetization tilted by an angle of 25° with respect to the direction of the ripples. The magnetization follows the Stoner-Wohlfarth model with a very narrow distribution in the direction of easy axis. It is suggested that, tilt of the easy axis can be understood in terms of the interplay of two shape anisotropy terms corresponding to the ensemble of strongly interacting nanocolumns through magnetostatic dipolar interaction, and the overall shape of a nanowire