Noise Mechanism of TDMR Readers at System Level

In perpendicular magnetic recording system, the jitter noise is the dominant noise from the medium. The jitter noise is proportional to the cross-track correlation and the square of transition parameter [1]. For a given head and medium, pushing linear density has more SNR penalty than increasing track density. That is why all the emerging technologies, such as shingled magnetic recording, microwave assisted magnetic recording, heat assisted magnetic recording, and bit pattern media, emphasize more on the track density increment for the growth of areal density. One challenge from narrower track width is the inter-track interference (ITI). In the two-dimensional magnetic recording (TDMR), multiple readers were proposed to reproduce the signals from multiple tracks [2]. The recent study shows that TDMR readers are effective to cancel the ITI from the adjacent tracks and are able to achieve higher track density [3]. The pitch between the readers along cross-track direction needs to be set properly for the optimal ITI cancellation. But due to the skew angle, one of TDMR readers may have to read near the middle of two tracks. When the recording bits on two adjacent tracks are in the opposite polarity, it may create local flux paths between reader hard bias and medium bits. This could generate multi-domains in the read sensor and produces additional reader noises. This paper studies this noise dependence on both the off-track position and the bit length.