Exchange coupled composite media for perpendicular recording

For conventional perpendicular recording media of saturation magnetization M/sub S/ and grain volume V, the ratio of the stabilizing energy barrier /spl Delta/E to the switching field H/sub S/ is /spl xi/=2/spl Delta/E/(M/sub S/H/sub S/V)=1, in contrast to a value of 2 for the case of anisotropy axes tilted at an angle of 45/spl deg/. This means only half the possible resistance to superparamagnetism is gained; it makes writability a serious problem for high density perpendicular media when a large anisotropy is used to compensate decreased grain size. To address this problem, an exchange coupled composite perpendicular recording media has been proposed that increases /spl xi/ by a factor of two, as in 45/spl deg/ tilted media, but reduces some of the difficulties, particularly in fabrication.