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• Nanomagnetics
• Atomic scale characterization & fabrication
• Modeling nanostructures in mesoscopic environments
• Nanoscale measurement & fabrication using laser-controlled atoms
• Atom Optics
• Magneto-Optic Microscopy
• Magnetic Force Microscopy
• Nanoscale Physics
• SEMPA
• UHV STM

Magnetic Microstructure of Recording Media

The bit density of information stored on magnetic hard disks continues to increase at a rapid pace and the characteristic size of the bits written on such disks shrinks accordingly. Consequently, new measurement techniques with very high sensitivity and spatial resolution are needed with which to characterize the fundamental magnetic properties of both recording media and of read/write heads and to study the interaction of the heads with the media. Magnetic imaging with SEMPA has proven to be a valuable technique for the microscopic characterization of these systems.

SEMPA image of a test pattern This figure shows a SEMPA image of a test pattern with variable bit density written on CoPtCr media. The written tracks are about 9 µm wide with a 1 µmm spacing between them, corresponding to a track density of about 2.5 KTPI (thousand tracks per inch). The largest bits are about 10 µmm wide. The smallest bits in the image (not visible at this resolution) are about 0.2 µmm wide, corresponding to a bit density of about 125 KFCI (kilo flux changes per inch). These smallest bits would represent a storage density of about 300 Mbits/in2. For reference, the goal of the magnetic storage industry is to achieve 10 Gbit/in2 by about 1998. To reach that goal, bits about 0.085 µmm wide must be written on tracks about 1 µmm wide. Significant advances in current magnetic measurement technology will be required to characterize heads and media at that length scale.

higher resolution SEMPA image This figure shows a higher resolution SEMPA image of test bits written onto another sample disk. These bits, about 0.13 µmm wide (200 KFCI) in a track about 3 µmm wide (8.5 KTPI), represent a storage density of about 1.7 Gbit/in2. Magnetic images such as these provide important information about the quality of the written bits, their edge acuity, distortions along the track edge, and other important characteristics which contribute to the fidelity with which magnetic information can be written and retrieved.



Staff listing
John Unguris
Robert J. Celotta
Daniel T. Pierce

Former staff listing
Andrew Gavrin - Indiana University - Purdue University at Indiana
Michael Kelley - NIST
Michael Scheinfein - Arizona State
David Tulchinsky - Naval Research Laboratory

Collaborators listing
National Storage Industry Consortium

Supported in part by the Office of Naval Research

Online: May 1996
Last Updated: February 2008

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