Hard Drive Density Continues to Grow at Amazing Pace

By Will Greenwald

New magnetic recording technique may let hard drive platters store 1 terabyte per square inch.

Last week, Nature Photonic published a paper that outlines a new magnetic recording technique that can readily store up to 1 terabyte per square inch. The researchers, all employees of Hitachi, describe a "plasmonic nano-antenna" built into a magnetic recording head that would allow for such storage density in magnetic media. The technique combines two already-established recording methods, thermally-assisted magnetic (TAR) and bit-patterned recording (BPR).  
The two methods are intended to reduce the effects of supermagnetism, where the heat produced by writing a bit can change nearby bits and damage data. TAR heats a small-grain area of the media to write the bit, then cools it rapidly, using the heat itself and the space between bits to reduce or eliminate supermagnetism. BPR writes to media with lithographed "magnetic islands" that physically isolate writing and prevent supermagnetism from affecting surrounding bits. While they address the problem of supermagnetism, they each have their own limitations and can only fit 200-300GB per square inch onto media. TAR requires small-grained media, while BRP needs to use a write head that exactly fits the size of the media's islands. 
In the new technique, the plasmonic nano-antenna's unique shape brings together the best facets of both TAR and BPR. The antenna is shaped like an E, with the outer prongs grounding the antenna while the center prong carries the charge. With this design, the antenna can write bits to very small areas without affecting nearby bits, all on relatively inexpensive media. The technology was demonstrated to be stable at 1TB per square inch, but the researchers say they can theoretically increase memory density to ten times that much. 

perpendicular recording. Previously, hard drives had used longitudinal recording, which aligned bits to the surface of the disc. In perpendicular recording, the bits are aligned perpendicular to the surface of the disc, allowing for a higher bit density. In 2005, Toshiba released the first hard drive to use this technique, a 1.8-inch 80GB hard drive. Over the next few years, the hard drive industry further developed perpendicular recording and produced greater and greater bit density. In 2007, Hitachi released the first 1TB hard drive, built with five 200GB platters. Two years later, Western Digital doubles that with a 2TB hard drive consisting of four 500GB platters. Most recently, TDK has been getting ready to release the world's first 3TB hard drive, using 640GB platters. 
In just four years, the amount of feasible storage space in a 3.5-inch hard drive has tripled from 1TB to 3TB. To put that in perspective, hard drives only broke the 137GB storage barrier in nine years ago. That's a 2100% increase in hard drive space in less than a decade. If Hitachi's new method proves feasible on a consumer level, that curve can only grow steeper and steeper.