IBM, Fujifilm tweak BaFe particles for record magnetic tape data density


Researchers at IBM in Zurich have achieved a world record in areal data density on linear magnetic tape, updating what is still a reliable long-term storage technology despite the rise of digital and optical storage media.

Tape-based storage is used to store up to petabytes of information, at as little as 1/10th the cost of hard disk drive (HDD) storage systems, and is far more energy efficient; many corporations (especially older ones) still use plenty of tape backup.

In work with Japan's Fujifilm, the researchers recorded data on a prototype tape at a density of 29.5 billion bits/in2, about 39× the areal data density of today's industry-standard magnetic tapes. Key to the work was development of "several new critical technologies," including:

• A new dual-coat magnetic tape based on barium ferrite (BaFe) particles, developed by Fujifilm "in close collaboration" with IBM. The tape uses ultrafine perpendicularly-oriented BaFe magnetic medium without using expensive metal sputtering- or evaporation-coating methods. Fujitsu separately described its contribution: A new dispersion material was used to control agglomeration of micrified particles—achieving microparticulation of BaFe particles to 1600nm (about one-third the size of current metal particles), with uniform dispersion and uniform coating of super-smooth thin magnetic layer.

• Three new servo control technologies that increase by 25-fold the number of data tracks on a half-inch-wide tape: a new servo pattern to enable high-bandwidth nanometer-scale position information, a new method for detecting and decoding position information in the servo pattern, and state-space-based control concepts. Together these enable track-follow performance of <24nm standard deviation, and reduce track width to <0.45nm.

• Signal-processing algorithms for the data channel—an advanced data read channel based on a new data-dependent noise-predictive, maximum-likelihood (DD-NPML) detection scheme, to enable accurate detection of data despite reduced signal-to-noise ratio (from using an ultranarrow 0.2µm data reader head). Linear density increase of <50% relative to today's IBM LTO Gen4 cartridge was achieved.

• Two new low-friction giant magnetoresistive (GMR) read/write head assemblies—a reduced-friction head assembly enabling smoother magnetic tapes, and a GMR head module incorporating optimized servo readers.

"This exciting achievement shows that tape storage is alive and strong and will continue to provide users reliable data protection, while maintaining a cost advantage over other storage technologies, including hard disk drives and flash," said Cindy Grossman, VP of IBM's tape and archive storage systems unit, in a statement.

Ultimately the goal is tape areal recording densities of 100 billion bits/in2, to keep up with the endless and rising tide of digital information. The researchers envision cartridges that can store up to 35 terabytes of uncompressed data, about 44× the capacity of IBM's LTO Gen4 cartridge—enough to store 35 million books, the real-world equivalent of nearly 250 miles of library bookshelves. — J.M.

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