GG-06: Bit-Island Arrangement and Signal Processing in Double-Layer Magnetic Recording Technology

To overcome the superparamagnetic limitation [1]-[2] that is the barrier to increasing the areal density (AD) of perpendicular magnetic recording technology, bit-patterned magnetic recording (BPMR) has been presented and applied together with the double layer magnetic recording (DLMR) [3]-[5]. Those works reveal the possibility and potential of DLMR to continuously increase AD. In this work; therefore, we first propose a DLMR structure that is designed based on bit-patterned media as shown in Fig. 1. The bit islands are aligned with a rectangular grid but the relative positions of each layer were shifted at the along- and cross-track directions by Tx/2 and Tz/2, respectively. On the top view, we have staggered-like recording media [6]. Then, we also present the use of an array reader that consists of three readheads in reading process, the way to retrieve all three readback signals will be described. The first (H1) and third (H3) readheads are positioned at the center of the l-th and l+2-th tracks (upper layer), respectively. The second readhead (H2) is positioned over the middle of the l+1-th track (lower layer). To evaluate the BER performance between our proposed media design under equivalent AD of 4.0 Tb/in2 (2.0+2.0 Tb/in2) denoted by “Prop. System” with the conventional single-layer bit-patterned media under AD of 4.0 Tb/in2 denoted by “Conv. System” as shown in Fig. 2. BER performances of the 1st, 2nd, and 3rd tracks are denoted by “Prop. System. H1 (UL)”, “Prop. System. H2 (LL),” and “Prop. System. H3 (UL), respectively. The average BER of three data tracks is denoted by “Prop. System. Avg.” The BER performances of the 1st and 3rd tracks are great because of lower ITI interference. On the other hand, the performance of the 2nd track is degraded by ILI effect. It implies that the proposed media structure based on a double-layer magnetic recording can enhance performance. Moreover, in this work, the optimal diameter of bit islands for each layer and the coding schemes will be also examined for avoiding ISI, ITI, and ILI effects.References: [1] C. Ross, Annual Review of Materials Research, 31(1). pp. 203-235 (2001) [2] R. L. White et al., IEEE Trans. Magn., pp. 990-995 (1997) [3] Y. Nakamura et al., 2021 IEEE INTERMAG, LYON, France, pp. 1-5 (2021) [4] H. Saito, IEEE Trans. Magn., 59(3), 3000810 (2023) [5] Y. Nakamura et al., IEEE Trans. Magn., 58, pp. 1-5 (2022) [6] Y. Ng et al., IEEE Trans. Magn. 48(6), pp. 1976-1983 (2012)