Precise noise characterization of perpendicular recording media

Abstract

Perpendicular recording is one of the technology candidates to extend the areal density growth trend with the superior thermal stability and the high recording resolution. As we have experienced with longitudinal recording, noise originating from perpendicular recording also has a strong impact on the channel performance. In this study, the noise characteristics of the readout waveforms of a tri-layer perpendicular media and single-pole write/MR read heads were investigated using precise time-domain analysis. Waveform fluctuations were obtained by subtracting the ensemble-averaged signal from each measured noise-contaminated waveform. The time-domain analysis makes clear the dominant type of transition-related noise such as transition jitter, pulse breathing or dc noise, etc. It was revealed that the noise from perpendicularly recording medium concentrates at the center of written transitions. The dominant transition noise source was found to be the transition position jitter. The level of transition jitter of the perpendicular media used in this study was found to be comparable to that of 5 Gbpsi class longitudinal media. MFM measurements revealed that magnetization fluctuates in large size of about 80 nm, which results in the fluctuation of the transition centerline. Reducing transition jitter should be the focus of developing future high performance perpendicular recording media.

Comparative evaluation of performance of percolated perpendicular media using FePt–MgO/Pt/Cr trilayer and FePt–MgO/MgO bilayer

“…Transition jitter noise [5,6] becomes a serious problem because grain size reduction is limited. A percolated perpendicular medium (PPM) has been proposed to increase the resolution of the signal without sacrificing thermal stability [7].…”

Percolated perpendicular medium of FePt‐MgO/MgO bilayer films for ultra‐high magnetic recording

“…The characteristic feature of CoCrPt-SiO 2 granular perpendicular medium (GPM) is its improved recording density with higher thermal stability and better recording resolution. However, the area density of CoCrPt-SiO 2 GPM cannot be increased arbitrarily; it is observed that the area density above 500 Gb/in 2 causes thermal instability and increased transition jitter noise [5][6][7]. In order to further increase the area recording density, the magnetic grain size must be further scaled down to less than 7 nm to reduce transition jitter noise while simultaneously maintaining a sufficient medium signal-to-noise ratio (SNR).…”

Correlation between transition parameter and transition jitter using Voronoi cell modeling

“…Previously, we revealed that transition jitter noise is dominant and is determined by magnetic cluster size in perpendicular magnetic recording [1,2]. Then we used Voronoi cells in order to express magnetic grain size or magnetic cluster size.…”