Numerical simulations show how to avoid imperfections in next generation of high-density data storage

May 08, 2013
Data storage: Synchronized at the write time
A scanning electron microscope image of a bit-patterned recording medium, with ordered arrays of magnetic islands. Credit: 2013 A*STAR Data Storage Institute

The rise of the internet and the move from paper to digital information has driven a need for large-volume electronic data storage. Maria Yu Lin and her co‐workers at the A*STAR Data Storage Institute, Singapore, have now established some important design principles to consider when developing bit patterned media recording (BPMR)—a potential high-density magnetic recording system of the future.

Conventional hard disk drives store a single data bit in a continuous magnetic medium consisting of many 'grains'. However, the number (approximately 10–15) and the size of these grains (about 6–10 ) naturally limits the maximum density at which digital information can be stored. The BPMR technique offers much higher because it records the data in a regular array of single-grain (see image) that can be much smaller than multiple grain bits in continuous media, according to Lin.

"Multiple grains must be used per data bit in continuous-," she explains. "Ideally, bit-patterned media [will] achieve one grain per bit because the are patterned in isolated and ordered arrays known as 'islands'."

A number of practical hurdles, however, are preventing the use of BPMR in computer hard disks. One problem is that the islands are separated by non-magnetic spaces—some 25–65% of the surface only is magnetic. The data can be passed from the writing `head' only when it is aligned with an island on the spinning disk. Therefore the writing process must be synchronized with the position of the magnetic islands. However, manufacturing defects, variations in disk spinning speed and vibrations can all cause temporal misalignment, which in turn causes writing errors.

Adding information to the disk that tells the writing head its exact position is one way to correctly time the writing process. This includes synchronization sectors and error correction information; however, this information reduces the capacity of the disk for data . Lin and co-workers used computer simulations to theoretically analyze the optimum number of the synchronization sectors. They also analyzed how the additional information would relate to variations in disk spin speed. They investigated the system with read/write spindle motors suffering from high, medium, low and zero speed variation.

"The analysis indicates that the total additional information needed for synchronization and error correction for a motor with a medium rotation variation is 11.75%," says Lin. "Compared to the potential gain in terms of data density that this technology enables, such a total overhead is acceptable."

Explore further: New terahertz device could strengthen security

More information: Lin, M. et al. Modeling for write synchronization in bit patterned media recording. Journal of Applied Physics 111, 07B918 (2012). dx.doi.org/10.1063/1.3679022

Lin, M. et al. Channel characterization and performance evaluation of bit-patterned media. IEEE Transactions on Magnetics 49, 723–729 (2013). ieeexplore.ieee.org/xpl/articl… jsp?arnumber=6416988

add to favorites email to friend print save as pdf

Related Stories

Toshiba makes a breakthrough in hard-drive capacity

Aug 23, 2010

(PhysOrg.com) -- Last Wednesday Toshiba made an announcement at the Magnetic Recording Conference in San Diego that they have made a breakthrough in their research of bit-patterned media that would result ...

Recommended for you

New terahertz device could strengthen security

Nov 21, 2014

We are all familiar with the hassles that accompany air travel. We shuffle through long lines, remove our shoes, and carry liquids in regulation-sized tubes. And even after all the effort, we still wonder if these procedures ...

CERN makes public first data of LHC experiments

Nov 21, 2014

CERN today launched its Open Data Portal where data from real collision events, produced by experiments at the Large Hadron Collider (LHC) will for the first time be made openly available to all. It is expected ...

New technique allows ultrasound to penetrate bone, metal

Nov 20, 2014

Researchers from North Carolina State University have developed a technique that allows ultrasound to penetrate bone or metal, using customized structures that offset the distortion usually caused by these ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.