Technologies that store information in the form of magnetism on some type of material, whether wire, tape, or disk, have been around for more than a century. But almost since magnetic recording's invention, scientists have been striving for ways to improve it by making it more reliable and able to store ever larger amounts of content, rendering the technology smaller, cheaper, and more efficient. The ingenuity and inventiveness of Shunichi Iwasaki and Mark Kryder have accomplished those goals to a degree that the pioneers of recording could never have imagined.
The quest for higher density and more durable recording technology became critical as the computer's role in society rapidly expanded from scientific tool and curiosity to an indispensable, fully-integrated part of our everyday world. More and more data needed to be stored in ever smaller, ever faster ways. But each technique, each way of preserving signals and digital bits through magnetism, has its limitations. A piece of tape can only hold so many iron-laden particles or grains to be magnetized, and can retain its magnetism only for a certain time. Computer hard drives can only spin just so fast, or be read just so quickly. Even before the 20th century came to a close, it had become clear to scientists and engineers that the capacity of computer hard drives was fast approaching an ultimate limit—until Shunichi Iwasaki devised an ingenious new way to store magnetic data.
From the beginning of his engineering career in 1949 at Tokyo Tsushin Kogyo Ltd., later known as Sony, Iwasaki specialized in the technology of magnetic recording. He expanded on this interest after becoming a professor at Tohoku University, and throughout the next two decades made significant contributions including the development of metal-based tapes and high-density recording technologies. It was in the mid-1970s that he devised what would become his signature idea. Since the beginnings of magnetic recording, the magnetized grains on a tape or other medium were longitudinally, or horizontally, oriented. On tape, for instance, this means that each grain was situated parallel to the tape's length, a system known as longitudinal magnetic recording (LMR). Thus, the capacity of a given length of tape was determined by how many grains could fit within that two-dimensional area. Iwasaki's inspiration opened up the third dimension. He realized that if a magnetic medium could be magnetized perpendicular to its surface, more magnetic grains would fit within a given area, vastly increasing storage capacity. Such a technique also allows the use of recording media with higher magnetic coercivity that are less susceptible to magnetic degradation and loss of signal over time. Iwasaki had invented perpendicular magnetic recording (PMR). Despite the elegant beauty of Iwasaki's conception and a great deal of initial enthusiasm for its potential, ensuing leaps forward in LMR technologies pushed PMR to the background for a time, a period Iwasaki refers to as the technology's "Death Valley." Iwasaki kept the PMR fires burning by continuing to write papers and hold conferences on his ideas. Some three decades after he first announced the concept, PMR came of age—largely due to the efforts of Mark Kryder.
First as founder and director of Carnegie Mellon University's Data Storage Systems Center and then as director of research for Seagate, the largest hard disk drive manufacturer in the world, Kryder had been striving to increase the efficiency and capacity of computer memories. A 2005 Scientific American article on Kryder's work noted his observation that hard drive densities had been doubling roughly every 18 months, an idea that's become informally knows as "Kryder's law," after the famous "Moore's law" concerning the density of semiconductors on computer chips. As it happened, "Kryder's law" was too conservative. At Seagate, he led the research and development effort to transform Iwasaki's work from the lab into the commercial realm, pursuing a goal of achieving a storage density of 100 gigabits of data to a square inch of space. That milestone was met in 2003 and was quickly exceeded, opening the floodgates to the practical realization of PMR, with Seagate introducing the first mass-produced PMR hard drive in 2006. Already, virtually all hard disk drives operate with PMR principles, and some are now boasting capacities in the terabyte range. Even PMR has an ultimate capacity, however, and engineers are looking beyond. Although now retired from Seagate, as University Professor of Electrical and Computer Engineering at Carnegie Mellon, Kryder is leading the research and development of one of the most promising successors, heat-assisted magnetic recording (HAMR), in which a laser pulse briefly heats the recording material to increase its capacity. If HAMR can be made practical, terabyte disk drives may become as inexpensive and common as today's gigabyte drives.
The computers that landed humans on the Moon and guided space probes beyond the solar system filled entire rooms. Today, the smartphones in our pockets and laptops are far more powerful and hold far more data. The technologies of the near future will be even smaller and more versatile. None of it would be possible without the magnetic storage technologies invented and developed by Shunichi Iwasaki and Mark Kryder.
Information as of April 2014