GG-04: Recording Medium Configurations for Double-Layer Bit-Patterned Magnetic Recording

With the tremendous increase in the demand for larger storage capacity, new recording technologies are essential to support this ever-increasing demand. One of the promising technologies is bit-patterned magnetic recording (BPMR) [1]. Recently, ideas of increasing an areal density (AD) by stacking multiple recording mediums upward have been explored on a conventional medium [2]-[3]. To further maximize the storage capacity, BPMR system with a stack of two recording layers each of which is a bit-patterned medium has been investigated [4]-[5]. Since the lower layer is further from the read/write head, difficulty in the retrieval signal and processing of data from the lower layer is expected. In this work, we examine two distinct configurations of recording medium in BPMR system with double recording layers as shown in Fig. 1. Recording medium in the first configuration employs two layers containing rectangular close-packed arrays of circular islands. In contrast, hexagonally packed arrays of islands are considered in the second configuration. In both configurations, the centers of individual islands on the lower layer are positioned under the gaps between magnetic islands on the upper layer. Such an arrangement potentially mitigates inter-layer interference that may occur during the superposition of signals from the upper and lower layers in the readback waveforms as shown in Fig. 2. By utilizing oversampling, we simply achieve the separation of the individual layer signals since the centers of islands on both layers are not aligned with one another. This also allows the simultaneous processing of data from both layers during one-dimensional equalization and detection. In the early stages, simulation results indicate that the proposed configurations can deeply improve the bit error rate (BER) performance compared with the single-layer BPMR system, considering a total AD of 4 Tb/in2 and a perfect writing condition.References: [1] B.D. Terriset et al., Microsyst. 13(2), 189–196 (2006). [2] K. S. Chanet et al., IEEE Trans. Magn. 55(12), 1–16 (2019). [3] Y. Nakamura et al., IEEE Trans. Magn. 58(8), 1–4 (2022). [4] N. Rueangnetr et al., AIP Adv. 13 (3), 035104 (2023). [5] H. Saito, IEEE Trans. Magn, 59(3), 3000810 (2023).