The major challenge in technological applications of magnetic arrays for storage is to control the magnetic switching precisely. To achieve this one needs to have reproducible remanent state and, second, the switching process itself must be simple and reproducible. Only in very few cases with well-defined anisotropies does the reversal take place via a coherent rotation of the magnetization. More common, however, is that the reversal occurs via the domain formation at the ends of the element. For arbitrary shape nano-scale elongated elements, in general, it has been impossible to reliably calculate the field at which domain first forms from basic principles.
If the memory element is ring instead of elongated, the magnetization flux forms a closure in the circular mode and the problems associated with the ends of the linear elements are eliminated. The ring elements exhibit two different highly stable 'onion" states in addition to the vortex states. Two possible onion states, forward or reverse magnetized, can be realized at remanence and can be used for magnetic storage.
On the other hand, it has been suggested that the inverse structure, nonmagnetic antidots (same as negative dots) in magnetic media, could be a potential system f or magnetic recording with areal densities approaching 750 Gb/in2. The PI proposes the systematic experimental study of periodic antidot arrays to compare with theoretical predictions presently available. The investigation of the changes in the magnetic properties induced by the antidotes, different remanent states for antidotes of various shapes, influence of magnetocrystalline anisotropy, film thickness and possible application for high-density storage will be performed and the exploration of the high-density limits will be studied.
