High K-u materials approach to 100 Gbits/in(2)

High K-u, uniaxial magnetocrystalline anisotropy, materials are generally a ttractive for ultrahigh density magnetic recording applications as they all ow smaller, thermally stable media grains. Prominent candidates are rare-ea rth transition metals (Co5Sm,...) and tetragonal intermetallic compounds (L 1(0) 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 gra in diameters, D, and a potential 10-fold areal density increase (proportion al to 1 / D-2), well beyond the currently projected 40-100 Gbits/in(2) mark . Realization of such densities will depend on a large number of factors, n ot all related to solving media microstructure problems, In particular, it is at present not known how to record into such media, which may require wr ite fields in the order of 10-100 kOe. Despite this unsolved problem, there is considerable interest in high Ku alternative media, both for longitudin al and perpendicular recording. Activities in this area will be reviewed an d data on sputtered and evaporated thin FePt films, with coercivities excee ding 10000 Oe will be presented.