Micro-magnetic Study And Design Of Magnetic Data Storage System With Ultra-high Density

As the main supporter of the information storage, magnetic recording technology andmagnetic disk drives with low cost, high reliability and fast increased density, always pushforward the progess of information industry. When the recording density graduallyapproaches to1Tb/in2, how to break the density limit of conventional perpendicularmagnetic recording with new technologies, and push the density of magnetic disk drivefrom0.15~0.2Tb/in2in the begin year (2008) of this study to10Tb/in2–60times increase–in future15~20years is the research with widespread concern. In this dissertation, thefeasibility of achieving multi-Tb/in2magnetic data storage using patterned media recordingand shingled writing technology is explored through micromagnetic modeling. And the10Tb/in2shingled writing based patterned media recording system is designed in detail fromboth the magnetic head and magnetic recording media aspects. The head design includesthe writing head structure, writing corner angle, corner rounding effect, skew angle and thehigh-frequency responsibility, and the media design includes the recording media structure,magnetic properties and bit cell arrangement. This design provides a practicable progressscheme of key technologies in magnetic data storage.This research independently models the shingled writing head for10Tb/in2magneticrecording, and studies the effects of the head structure on the writing field and fieldgradient using micro-magnetic calculation. All the effects are also illustrated frommagnetism theory. Based on the simulation results, this paper originally reveals that thewriting field and field gradient around the writing corner of shingled writing head are moreimportant for achieving10Tb/in2magnetic recording, compared with the maximum writingfield, and the increasing trend of writing field will rapidly slow down as the pole tip widthincreases. Other head structures, such as pole tip tapered angle, shield gap length and poletip height, need to be set at reasonable levels to achieve10Tb/in2shingled magneticrecording.This work derives the recording performance calculation method of shingled writing based patterned media recording system. The effects of writing head with different writing corneron the recording performance are calculated and compared, and the optimal writing cornerangle is suggested from the consideration of decreasing the write-in error rate. Furthermore,the “corner rounding effect” of shingled writing head is also studied. The influence ofdifferent rounded writing corners upon the recording performance is calculated throughmicro-magnetic modeling, and the results show that the writing head with small roundedcorner is benefit for the write-in error rate decrease of10Tb/in2shingled magneticrecording system.The maximum erasing error rate of10Tb/in2shingled magnetic recording system withdifferent skew angle range is studied through micro-magnetic calculation. The results showthat reducing the skew angle range is benefit for improving the writing performance whenrecording density increases. Therefore, this work proposes the dual-corner shingled writingtechnology for reducing skew angle range. Using this writing method, the skew angle rangeof each writing corner can be reduced into10°and the recording performance of shingledrecording system can be fundamentally increased.The reversal requirements of patterned bit cell are calculated under the practical writingfield distribution. The high-frequency response characters of10Tb/in2shingled writinghead are also studied. The simulation results reveal that increasing the damping constant ofrecording media is an effective way to enchance the high-frequency response performanceof10Tb/in2shingled magnetic recording system. The shingled writing head is alsodesigned in detail to satisfy the high-frequency response requirements.The magneto-static interference of surrounding patterned bit cells in different bit cellarrangements and manufacturing induced deviations is studied. Commonly used bit cellarrangements are categorized into three representative types: square arrangement, isoscelestriangular arrangement and equilateral triangular arrangement. Compared with other twoarrangements, the equilateral case introduces strongest cell-to-cell interference and showsthe greatest sensitivity to manufacturing induced deviations. The isosceles triangulararrangement is a recommended approach in terms of reducing the possible switch fielddistribution broadening, caused by manufacturing induced bit cell position offset and bitcell size variation, without introducing extra track positioning accuracy requirement.