High Ku materials approach to 100 Gbits/in2

High K_u, uniaxial magnetocrystalline anisotropy, materials are generally attractive for ultrahigh density magnetic recording applications as they allow smaller, thermally stable media grains. Prominent candidates are rare-earth transition metals (Co₅Sm,...), and tetragonal intermetallic compounds (L1₀ phases FePt, CoPtY,...), which have 20-40 times higher K_u than today´s hexagonal Co-alloy based media. This allows for about 3 times smaller grain diameters, D, and a potential 10-fold areal density increase (∝1/D²), well beyond the currently projected 40-100 Gbits/in² mark, Realization of such densities will depend on a large number of factors, not all related to solving media microstructure problems, In particular it is at present not known how to record into such media, which may require write fields in the order of 10-100 kOe. Despite this unsolved problem, there is considerable interest in high Ku alternative media, both for longitudinal and perpendicular recording. Activities in this area will be reviewed and data on sputtered and evaporated thin FePt films, with coercivities exceeding 10000 Oe will be presented.