Domain Shape of CGC-like Films with Under Layer of Periodic Isolated FePt Particles

Abstract

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).