Nanomagnets for sensors and data storage

Miniaturized magnetic devices are ubiquitous in the hard disks of computers and in tape storage systems. Giant magnetoresistance was discovered as rec ently as 1988 but already sensors using the effect are being incorporated i nto read heads for the highest density hard disk systems. As a result of in tensive research and development, storage density on hard disks has increas ed dramatically at a rate greater than 60% per year. At sub-micron and nano -scale dimensions the properties of magnetic devices are strongly affected by their size and shape in a complex way resulting from the interplay betwe en different types of magnetic energy. In some cases this causes a deterior ation in the performance of existing devices, however it has also enabled e ntirely new devices to be proposed. Arrays of nanomagnets could be used for ultra-high density storage on hard disks or for fast and dense, non-volati le, solid state memory. Storage applications are possible because hysteresi s in the nanomagnets creates two oppositely magnetized states which are sta ble in zero applied field and can store binary data. Magnetic sensors based on giant magnetoresistance in layered magnetic structures are among the mo st sensitive available for operation at room temperature and above. This pa per describes the physical properties of nanomagnets and their role in pres ent and future applications.