Optimization of Soft Layer Uniaxial Anisotropy Gradient in Media for Microwave-Assisted Magnetic Recording

Exchange-coupled composite (ECC), notched, and graded anisotropy recording media were optimized for microwave-assisted magnetic recording at head-medium spacings from 4.5 to 14.5 nm. When the average value of uniaxial anisotropy (
$K_{u}$
) in the soft layer was low, notched media gave the best recording performance. As the average soft layer
$K_{u}$
increased, first ECC and then graded anisotropy media became optimal. When the hard layer
$K_{u}$
was high, notched media outperformed graded anisotropy media. However, the performance of graded anisotropy media improved as the hard layer
$K_{u}$
was reduced, and when the hard layer
$K_{u}$
was sufficiently small, graded anisotropy media were preferred.