Effects of substrate eddy current on magnetic anisotropy in permalloy underlayer for perpendicular media

A new method to prepare permalloy film on a disk substrate with an easy magnetization axis in the radial direction is described. The permalloy film is sputter-deposited under radial magnetic field from concentric circumferential eddy currents in an aluminum disk substrate. The eddy current is produced by applying an AC magnetic field perpendicular to the substrate. With a perpendicular magnetic field of 50 Hz and approximately 15 Oe, a radial magnetic field of 2 Oe was created on a 5.25 ′′ substrate, which was sufficiently large to align the easy axis of 1-µm-thick permalloy film in the radial direction.