The crossover from antidot to dot magnetic behavior on arrays patterned in a ferromagnetic thin film has been achieved by modifying only the geometry. A series of antidot arrays has been fabricated on cobalt with fixed diameter $d$ and by reducing the period of the array $p$ from $p\gg d$ to $p<d$. A dramatic change in the coercivity dependence with $p$, correlated with a significant modification in the magnetic domain structure observed by x-ray photoemission electron microscopy, evidences the crossover. An intermediate regime has been found between the superdomain structure present in antidot arrays and the array of astroid-state noncorrelated dots. The study has been reproduced for a different ferromagnetic material, permalloy, and supported by micromagnetic simulations. DOI: http://dx.doi.org/10.1103/PhysRevB.89.144405 ©2014 American Physical Society

Within a simple model, we study magnetic domain walls (DWs) inside the inner core of the amorphous ferromagnetic microwire whose spin ordering is a core-shell structure. The interaction of the (internal stress created) outer shell of the wire on the inner core is included into the Landau-Lifshitz equation via an effective Dzyaloshinskii-Moriya-like anisotropy. The resulting DW textures are classified. The model is applicable to the nanowires of a modulated diameter (periodically constricted nanowires) as well. In that case, a core-shell magnetic structure is of the purely magnetostatic origin. Because the micromagnetic simulations of the microwires are extremely challenging, the simulations of the structured nanowires are performed with the purpose of verifying analytical predictions on the shape of the DW.

Investigations of geometric frustrations in magnetic antidot lattices have led to the observation of interesting phenomena like spin-ice and magnetic monopoles. By using highly focused magneto-optical Kerr effect measurements and x-ray microscopy with magnetic contrast we deduce that geometrical frustration in these nanostructured thin film systems also leads to an out-of-plane magnetization from a purely in-plane applied magnetic field. For certain orientations of the antidot lattice, formation of perpendicular magnetic domains has been found with a size of several μm that may be used for an in-plane/out-of-plane transducer.

We report the investigations on the giant magnetoimpedance (GMI) effect and the surface magnetic structure performed in the series of glass covered Co-rich amorphous microwires with different thicknesses of glass covering. The calculation of the surface hysteresis loops has been performed in the frames of the model which takes into account the helical magnetic anisotropy. The correlation between the value of the GMI ratio, the jump of the circular magnetization, and the value of the angle of helical anisotropy has been established. It was found that the angle of the surface helical anisotropy, for which the highest value of GMI, is close to 60°.