Hierarchical Recording Architecture for Three-Dimensional Magnetic Recording

TL;DR

Three-dimensional magnetic recording (3DMR) can dramatically expand HDD capacity by stacking recording layers, but ensuring sequential, correct writing across layers is challenging. The authors propose a hierarchical recording architecture with layered heat-assisted writing and a multi-head array, validated by micromagnetic simulations of a dual-layer FePt medium solving the Landau-Lifshitz-Bloch dynamics under spatially varying temperature and field profiles. They report high layer-specific switching probability and a non-monotonic but optimizable medium SNR, identifying an optimal head separation $\Delta d_{opt}$ and illustrating the reversal mechanism across passes. This approach demonstrates a feasible path to scale 3DMR to more layers, offering a route to ultra-high-capacity storage with controllable noise performance.

Abstract

Three-dimensional magnetic recording (3DMR) is a highly promising approach to achieving ultra-large data storage capacity in hard disk drives. One of the greatest challenges for 3DMR lies in performing sequential and correct writing of bits into the multi-layer recording medium. In this work, we have proposed a hierarchical recording architecture based on layered heat-assisted writing with a multi-head array. The feasibility of the architecture is validated in a dual-layer 3DMR system with FePt-based thin films via micromagnetic simulation. Our results reveal the magnetization reversal mechanism of the grains, ultimately attaining appreciable switching probability and medium signal-to-noise ratio (SNR) for each layer. In particular, an optimal head-to-head distance is identified as the one that maximizes the medium SNR. Optimizing the system's noise resistance will improve the overall SNR and allow for a smaller optimal head-to-head distance, which can pave the way for scaling 3DMR to more recording layers.

Figures (7)

• Figure 1: Structure and major components of the 3DMR media.
• Figure 2: (a) Schematic diagram of the layered heat-assisted writing process in 3DMR. (b) Temperature dependencies of coercivity for different layers.
• Figure 3: Schematic diagram of the hierarchical recording architecture with a multi-head array for 3DMR.
• Figure 4: The results for either the top or bottom layer after individual heat-assisted writing. (a) The distribution of the $z$-axis normalized magnetization $m_z$ of grains in the $xy$ plane. (b) The $z$-axis normalized magnetization and the writing field along the down-track direction, $m_z(x)$ (solid line) and $H_w(x)$ (dashed line). Pink and gray represent the actual and ideal switching regions on the track, respectively.
• Figure 5: The dependence of effective switching possibility $SP_{\rm eff}$ on writing field for the top (yellow line) and bottom (green line) layers.