High Recording Performance of Bit-Patterned Media With Two-Layer Inclined Anisotropy ECC Dots

A simplified exchange coupled composite (ECC) dot structure with a reduced switching field and small applied field angle dependence in the switching field is proposed. It was found from a spin model analysis that a reduced switching field as well as a small applied field angle dependence of the field is obtainable even for two-layer ECC dot when the anisotropy axis is weakly inclined with an increased anisotropy for the soft layer. The switching properties of the two-layer ECC dots were confirmed using a micromagnetic simulation. A minimum normalized switching field of 0.51 was obtained for a two-layer ECC dot model of stacked cubes with a size of 5 nm and an anisotropy inclination angle of 10°. Recording simulation on a bit-pattered medium of the two-layer ECC dot array suggested the possibility of a high areal density recording beyond 4 Tdot/in 2 by shingled recording. It was also confirmed by simulation that the proposed inclined anisotropy ECC dot could be applicable to granular media for narrow track recoding.