We reported simulated results of coupled granular and continuous (CGC)-like film, consisting of FePt granular under layer that act as a domain pinning of TbFeCo layer. For further increasing the recording density, grain diameter and period of each grain p have to be decreased until comparable scale with the domain wall width Wd and it causes difficulty to predict the domain structure. Simulated result shows it could be formed on p ≅ Wd (domain diameter Dd = 25 nm), which domain size is suitable to 1 Tbit/inch 2 . Moreover, we clarified that Dd = 22 nm (it is suitable at 1.33 Tbit/inch 2 ) at the TbFeCo surface and domain shape could be formed even under the condition of p < Wd. And we estimated the effective wall coercivity Hw from the simulation varying the applied magnetic field until domain is shrank and disappear. Suitable value of Hw ( >10kOe) was observed. Furthermore, to elucidate the details of this contribution by interfacial exchange coupling we carried out simulations while varying the values of interfacial exchange constant Aint over wide range. The observed pinning effect can be attributed to interfacial exchange coupling even much smaller value of Aint ( < 0.047×10 -6 erg/cm) comparing with A of TbFeCo (0.2×10 -6 erg/cm) and FePt (1.13×10 -6 erg/cm).

We report the simulated results for coupled granular and continuous (CGC) films for the thermo assisted magnetic recoding, consisting of FePt particles under layers that act as domain pinning sites of TbFeCo layers. As domain size should be smaller to further increase the recording density, the number of FePt grains has to be decreased in the domain. The simulated results demonstrated that they could be formed in a domain as small as 18.3 nm in diameter, which corresponds to a recording density of 1.8 Tbit/inch 2. Here, three FePt grains were effective for pinning. We also estimated the effective wall coercivity, Hw, from the simulation varying the applied magnetic field until a domain had shrunk and disappeared. The Hw was over 12 [KOe] where there were only three grains for pinning. The Hw was a function of the radius of the curvature at the pinning point and also the inverse average wall length between the pinning points in the same composite films.

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