Thermal stability dependence on the stacking order and thickness ratio of the CoPt–TiO2∕CoCrPt–SiO2 stacked media

Abstract

Thermal stability of the present CoCrPt–SiO2 media becomes a more critical issue as recording density steadily increases. In the present study, thermal stability of the stacked media composed of high Ku CoPt–TiO2 and normal Ku CoCrPt–SiO2 was studied by changing stacking order and thickness of each layer while keeping a constant total thickness. When the CoPt–TiO2 layer was placed under the CoCrPt–SiO2 layer, negative nucleation field and coercivity increased much more than those of the reverse stacking case. Thermal stability of the CoPt–TiO2 bottom group was superior to that of the CoCrPt–SiO2 bottom group when measured by a spin stand.

Grain geometry induced reversal behaviour alteration

“…For simplicity, they are assumed to be the same value. Uniaxial crystalline anisotropy of the soft magnet K U,t is varied from 0 to 5.0 × 10 5 J m −3 and that of the hard magnet is fixed to K U,b = 5.0 × 10 5 J m −3 , respectively [6,9]. Intragranular exchange constant A = 1×10 −11 J m −3 , intergranular exchange constant A int.exch is 2% of A, which corresponds to the intergranular exchange coupling strength J = 2 mJ m −2 , and the wetting angle ϕ is equally varied from 90 • to 150 • for the soft and hard materials.…”

“…In experimentally fabricated stacked structures, there are inconsistencies in oppositely stacked structures. In [6,7], it is reported that the stacked layer has higher coercivities than a single hard layer, and in some cases the bottom layer is magnetically harder than the upper layer or its saturation magnetization is smaller than the upper layer. The authors of [6] studied the behaviour as a viewpoint of the lattice distortion due to the contact of materials which have different lattice parameters.…”

“…In [6,7], it is reported that the stacked layer has higher coercivities than a single hard layer, and in some cases the bottom layer is magnetically harder than the upper layer or its saturation magnetization is smaller than the upper layer. The authors of [6] studied the behaviour as a viewpoint of the lattice distortion due to the contact of materials which have different lattice parameters. In this study, we focus on the influence of the convex and concave surfaces of the grains to explain the asymmetric magnetic switching behaviour.…”