Triangular arrays of submicrometer magnetic dots, with typical spacing of 400–600 nm and diameters close to 200 nm, have been fabricated by electron beam lithography to study pinning effects on Nb thin films. The resistivity versus magnetic field curves exhibit regular structure. Minima appear at constant field intervals, given by the lattice parameter of the dot array. The angular, current, and temperature dependencies of the resistivity imply synchronized pinning by the magnetic array which is relevant at high vortex velocities, when the order in the vortex lattice increases.

Vortex pinning in Nb thin films with rectangular submicrometric magnetic dot arrays exhibits interesting effects. Magnetotransport reveals the existence of two pinning regimes that correspond to two types of resistivity minima with different constant field intervals. The relation with the array lattice parameters indicates that a reconfiguration in the vortex lattice from rectangular to square is induced artificially by the interaction with the dot array. The transition occurs when the elastic energy of the vortex lattice becomes larger than the pinning energy provided by the artificial pinning sites. Using this reconfiguration the pinning energy associated with the magnetic dots can be estimated directly.

We have prepared regular square arrays of Ni and Ag dots with typical diameter and thickness approaching characteristic low-$T_c$ superconducting length scales. The transport properties of Nb films, grown on top of these dots, were studied in a wide temperature and magnetic-field range. The Ni dots act as pinning centers, thereby producing oscillations in the field dependence of the resistance and critical current of the Nb film. The periodicity of the oscillations corresponds to the matching field of the dots lattice spacing. Such an oscillatory behavior is absent for arrays of nonmagnetic Ag dots. The comparison between the two types of arrays implies a magnetic origin of the enhanced pinning effect.

Advances in nanoscale magnetism increasingly require characterization tools providing detailed descriptions of magnetic configurations. Magnetic transmission X-ray microscopy produces element specific magnetic domain images with nanometric lateral resolution in films up to ∼100 nm thick. Here we present an imaging method using the angular dependence of magnetic contrast in a series of high resolution transmission X-ray microscopy images to obtain quantitative descriptions of the magnetization (canting angles relative to surface normal and sense). This method is applied to 55–120 nm thick ferromagnetic NdCo₅ layers (canting angles between 65° and 22°), and to a NdCo₅ film covered with permalloy. Interestingly, permalloy induces a 43° rotation of Co magnetization towards surface normal. Our method allows identifying complex topological defects (merons or ½ skyrmions) in a NdCo₅ film that are only partially replicated by the permalloy overlayer. These results open possibilities for the characterization of deeply buried magnetic topological defects, nanostructures and devices.