Square nano-magnets as bit-patterned media with doubled possible data density

Due to their possible applications in magneto-electronic devices, nanostructured magnetic particles are one of the most important topics in recent research. In such low-dimensional systems, the shape anisotropy can significantly be increased, compared with magneto-crystalline and magneto-elastic anisotropies - and thus allows for tailoring magnetic properties by shape design. Especially square nanowire objects which can lead to stable intermediate states are of technical relevance. Such systems could be used as quaternary memory cells, i.e. for storing 2 bits per storage position, expanding the possible limits of Moore's law. Recent experimental investigations have revealed the influence of lateral dimensions, wall thicknesses, corner shapes, etc. on magnetization reversal mechanisms and corresponding hysteresis loop shapes, supported by micromagnetic simulations of such systems. The article provides an overview of previous theoretical and experimental results and gives an outlook to possible implementation of these nano-particles in novel hard-disk or MRAM technology.