# Writer Performance Optimization with Shingled Rounded Corner and Exchange Coupled Composite Media
## 1 Introduction  
When magnetic recording storage reaches ultra-high areal density, the recording media requires a larger anisotropy energy density (due to the smaller volume of each grain) to maintain thermal stability, and the writability needs to be enhanced to reverse the recording grain with a high anisotropy energy barrier, one of the feasible methods is to apply a shingled magnetic recording with ECC media [1; 2; 3]. The shingled magnetic recording technology has been applied in the manufacture of commercial hard drives. Currently Western Digital and Seagate companies have both launched the commercial hard drives based on shingled magnetic recording technology. Compared with conventional media, ECC media greatly decreases the switching field while maintaining almost the same thermal stability [4]. Composite media consists of a hard/soft magnetic bilayer structure, the hard layer with high anisotropy providing thermal stability while the soft layer with low anisotropy helps to switch the hard layer during the writing process, and it works through the quantum mechanical exchange coupling among magnetic layers [5; 6; 7; 8]. Meanwhile, it is known that shingled magnetic recording utilizes the pole tip with a relatively large write corner to switch recording bits, thus the write corner plays an important role in the write performance. However, the rounded corner is inevitable in the manufacturing process for the main pole of a shingled writer [2]. The write performances of a rotated single sense head and normally oriented single head with two-dimensional magnetic recording systems were investigated [9]. The multi-track detection scheme with a two-dimensional hybrid equalizer was developed to mitigate the impact of inter-track interference and media noise on the bit error rate performance [10]. The four-reader array detection architecture was proposed to recover the shingled recording data [11]. The novel read channel was modeled to capture the effects of inter-track and inter-symbol interference, and the neuralnetwork block predictor was presented to recover the recording information [12]. This research studies the effect of a shingled rounded corner writer on the write performance of SMR, which provides a guiding role on improving the writer design to reduce the erase band width. Figure 1a shows the 3D model of a shielded shingled rounded corner writer. Figure 1b shows the rounded corner from the air-bearing surface (ABS) view. As shown in Figure 1c, the rounded corner is characterized by two parameters in the model of a shingled rounded corner writer: the rounded angle (\(\theta\)) and corner length (\(L\)). The study indicates that during the writing process, the influence of a rounded corner causes the fluctuation of head field distribution around the write corner. Different structures of rounded corners cause variations of field gradients along the cross-track direction, which may lead to adjacent track erasure (ATE). This paper explores the impact of rounded corner writer design on the write performance of SMR with ECC media. First, the effect of writer structure on the write performance was investigated to reach a trade-off between adequate writability and field gradient. Specifically, the influence of the rounded corner effect on the write performance was evaluated by considering the variation of the write field gradient, the write-in error rate, and the erase band noise. Additionally, the EBWs of single-phase and ECC media were also studied and compared using the proposed EBW calculation method [13]. Furthermore, the influence of shield gap on the EBW was also discussed in this paper. Such an optimized shingled writer structure with a rounded corner was found to increase the field gradient and avoid the stray field-induced track erasure, which improves the write performance. Figure 1: (**a**) 3-D Model of shingled rounded corner writer; (**b**) Pole tip from ABS view. The main pole is half-wrapped around by shield; (**c**) Illustration of the rounded corner writer.