Probing interspatial magnetic flux distributions in ferromagnetic stripe arrays by specular and off-specular polarized neutron scattering

Abstract

Edge roughness in magnetic stripe arrays is an important structural parameter with a sizable impact on magnetic domains, domain correlation, pinning and propagation of domain walls in micro- and nanostripes proposed for data storage and logic devices. We have investigated two different stripe arrays fabricated by lithographic methods from permalloy ${\mathrm{Fe}}_{22}{\mathrm{Ni}}_{78}$, one with rough edges and another one with smooth edges. Performing polarized neutron reflectivity and polarized neutron off-specular scattering both patterns yield specular reflectivity curves with pronounced Kiessig fringes and well resolved Bragg bands in the off-specular regime due to the lateral periodicity. When applying a saturating magnetic field perpendicular to the stripes, a significant diffuse scattering can be detected close to the total reflection edge where it is enhanced by the Yoneda effect. This diffuse magnetic scattering can be attributed to inhomogeneities of the magnetic induction in the empty space between the stripes. In contrast, the sample with much less edge roughness does not exhibit off-specular diffuse scattering. Thus polarized neutron scattering from stripe patterns is a suitable tool for quantitative characterization of inhomogeneous magnetic flux distribution in the interspace between magnetic stripes invoked by their edge roughness.