Two-Dimensional Coding for Probe Recording on Magnetic Patterned Media

Abstract

The effect of intertrack intersymbol interference in a magnetic patterned medium is studied. A 2-D channel code is proposed, dedicated to perpendicularly magnetized media without soft underlayer, which exhibit read pulses showing overshoot. Read pulse shapes were investigated using a magnetic-force microscope tip scanning the patterned medium row by row. To test different codes, a bit-detection simulation program was developed to generate large amounts of data on which bit error rates can be measured. Application of the 2-D channel code, which implies recording of particular dot positions with fixed bits ("ones," "zeros") resulted in the elimination of 2-D worst case bit patterns and a subsequent reduction of detected-bit errors. The accompanying redundancy of 22% is inevitable for this type of 2-D code.Index Terms-Intertrack interference, magnetic force microscopy (MFM), patterned media, perpendicular magnetic recording, twodimensional coding.

A Two-Dimensional Code for Bit Patterned Magnetic Recording Channel

“…This prevents the situation in which all nine bits in a 3-by-3 array have the same value. The code rate of the proposed code is 7/8 which is higher than the previous conventional 7/9 and 5/6 channel codes in [10] and [11].…”

“…It places one parity bit with the value as opposed to adjacent bits among every 3-by-2 bit array. In [10], [11], the codes show better performance than no coding scheme. In this work, we propose a 2-D modulation code preventing the situation that all nine bits in a 3-by-3 bit array have the same values.…”

“…In other words, if the values of the data bits are all '0' bits or '1' bit in a 3-by-3 bit array, the amplitude of the center bit is much lower than its original amplitude [10]. Figure 1 illustrates the phenomenon.…”

“…[7][8][9] . Among those works, the 2-D channel codes have been designed to consider the patterned media by exploiting a probe recording scheme, unlike conventional magnetic recording [10,11] .…”

“…The proposed code has a higher code rate than the previous two codes. Read signals of (a) single bit, (b) "one" bit surrounded by eight "zero" bits, and (c) nine "one" bits [10]. This is illustrated in Fig.…”