Maximum Likelihood Detection for 3-D-MAMR

3-D magnetic recording is a candidate next-generation magnetic recording where multiple recording layers are used, each layer storing its own independent data, which has the potential to extend the storage areal density while having several challenges to overcome. On the writing side, one proposal is to use the microwave-assisted magnetic recording that energizes a particular layer in the stack with a field from a spin-torque oscillator to select a specific layer for writing. Readback is also a challenge as the standard reader picks up a superposition of signals from the multiple layers. The data from each layer have to be accurately recovered despite the high levels of interference between the layers. In this article, we assess the impact of such interference and look for ways to mitigate it to realize the gains of multilayer recording. We perform an initial study on the capacity of the summation of a pair of binary channels, followed by a model for a two-layer recording system with the lower layer having worse dispersion. Our study indicates the potential for some net areal-density gains from the introduction of the second layer that could lead to the increased longevity of the magnetic recording industry.