Measurements are reported on the magnetization reversal in submicron magnetic rings fabricated by high-resolution electron beam lithography and lift-off from cobalt thin films. For all dimensions investigated, with diameters of 300-800 nm and a thickness of 10-50 nm, the flux closure state is the stable magnetization configuration. However, with increasing diameter and decreasing film thickness a metastable near single domain state can be obtained during the reversal process in an in-plane applied field.

This review is intended as an introduction to mesomagnetism, with an emphasis on what the defining length scales and their origins are. It includes a brief introduction to the mathematics of domains and domain walls before examining the domain patterns and their stability in 1D and 2D confined magnetic structures. This is followed by an investigation of the effects of size and temperature on confined magnetic structures. Then, the relationship between mesomagnetism and the developing field of spin electronics is discussed. In particular, the various types of magnetoresistance, with an emphasis on the theory and applications of giant magnetoresistance and tunnelling magnetoresistance, are studied. Single electronics are briefly examined before concluding with an outlook on future developments in mesomagnetism.

Using ferromagnetic resonance, the angular dependence of the uniform precession mode of infinite cylinders is investigated at room temperature for low density Ni nanowire arrays, embedded in a polycarbonate membrane, with wire diameters ranging from 35 nm to 500 nm. All wires reveal a very similar behavior of the resonance field vs angle, independent of the wire diameter and wire density, corresponding to the uniform precession mode of an infinite cylinder including the shape demagnetization anisotropy and a small uniaxial anisotropy contribution. From the analysis of the angular dependence of the linewidth, the distribution of the wire orientation and the effective anisotropy field can be estimated. The latter is broadened due to the presence of a sub-structure in the absorption spectra.

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Nucleation and annihilation of vortex states have been studied in two-dimensional arrays of densely packed cobalt dots. A clear signature of dipolar interactions both between single-domain state dots and vortex state dots has been observed from the dependence of vortex nucleation and annihilation fields on interdot separation. A direct consequence of these interactions is the formation of vortex chains as well as dipole chains aligned along the direction of the external field. In addition, short range correlation of chiralities within vortex chains has been observed using magnetic force microscopy imaging and has been attributed to cross-talking between adjacent elements.