Reader Design for Bit Patterned Media Recording at 10 Tb/in$^{2}$ Density

Two-Dimensional Magnetic Recording With a Novel Write Precompensation Scheme for 2-D Nonlinear Transition Shift

“…An RHA combined with oversampled signal processing is used for readback, which achieves a great performance improvement compared with the normally oriented head array for readback at ultrahigh recording density [7], [8]. A schematic drawing of an RHA is shown in Fig.…”

“…It is important to note that the multitrack output was still used to 2-D equalize the main track into a negligible ITI and controllable ISI 1-D target. Here, the ITI becomes less severe due to the 2-D equalization and the arrangement of the RHA [7], [8]. After the equalizer, a conventional four-state 1-D Viterbi detector is implemented.…”

“…8 (8) and (9), as shown at the bottom of the page, where H m,n d (x, y) is the demagnetizing field produced by the previous written bits at the (m, n)th bit, {x, y} are the coordinates within the evaluation plane, which is divided with a 1 nm mesh grid, H i, j mag is the demagnetizing field produced by the (i, j)th bit, and N m,n is the range of the demagnetizing field calculation. Here, d m,n i, j is the distance between the center of (i, j)th bit and the (m, n)th bit, and d 0 = 100 nm, which is the critical range where the magnetostatic field is considered.…”

“…This scheme calculates the needed optimum write field for the current transition being written by subtracting the demagnetizing field produced by the previous written transitions from a fixed write field and determines the optimum writing current based on the minimum mean-squared error (MMSE) between the needed field and the available fields using an established field library. This write precompensation scheme is tested with a realistic micromagnetic writer and media and readback with a rotated reader array (RHA) [7], [8] combined with a read channel. Simulation indicates that the proposed write precompensation technique can decrease BER about one half compared with the case without write precompensation and approach the performance of the system with negligible NLTS, increasing the user areal density (UAD) from 3.2 to 4.1 Tbits/in 2 for a TDMR system with 8 nm Voronoi grains.…”

Two-Dimensional Magnetic Recording Using a Rotated Head Array and LDPC Code Decoding

“…1(b), combined with oversampled signal processing, was proposed for readback at ultra-high density from both granular media [5] and bit patterned media [7] with perfect writing. Here, a conventional giant magnetoresistance (GMR)-based head is used, and the dimension of the free layer is 18 nm × 18 nm × 4 nm, shield-to-shield spacing is 11 nm and magnetic fly height is 3 nm.…”