Medium Layer Structure in Three-Dimensional Heat-Assisted Magnetic Recording

We examine a medium layer structure in three-dimensional heat-assisted magnetic recording (3D HAMR) at 2 Tbpsi per layer (total density of 4 Tbpsi) where the medium consists of a high Curie temperature (HC) layer and a low Curie temperature (LC) layer. We perform a heat transfer simulation for 3D HAMR media including the isolation layer. To evaluate the grain error distribution, the expected value of the magnetization is calculated using the grain error probability. The error threshold and the time dependence of the bit error rate are discussed for 10 years of archiving. The information stability in the HC layer while writing in the LC layer is estimated using the temperature profile calculated by the heat transfer simulation. An LC (upper, namely, surface) / HC (lower) layer structure is compared with an HC (upper) / LC (lower) layer structure. The former is disadvantageous in relation to the medium surface temperature as regards writing in the HC layer. The latter may be disadvantageous in relation to the difference between the thermal gradients for HC and LC writing.