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Icons of Progress

The Invention of the Rewritable Magneto-Optical Disk

IBM100 The Invention of the Rewritable Magneto-Optical Disk iconic mark

In 1972, three IBM scientists working out of the Thomas J. Watson Research Center in Yorktown, NY, found a combination of two common minerals and a rare earth element that could be easily and repeatedly magnetized to accept large volumes of computer data at high speeds.

The question was, “What to do with it?” It would take five more years of hard work to find the answer to that question. Their immediate thought was that their discovery would revolutionize computer hard drives by dramatically increasing their capacity to hold data and by lowering their cost. But it didn’t work out that way.

Instead, their work forever changed the world of storage, creating a substantial enterprise industry built around the invention of what would become known commercially as the rewritable optical disk or the magneto-optical disk. Their story became a milestone in IBM’s long history of data storage innovations that have transformed industries across the world.

At the time of their discovery, the three researchers had been chasing Bell Labs, the early leader in the search for a new form of non-volatile computer storage called Bubble Memory. The bubble name came from tiny circles of magnetic fields, called domains, which formed in the new, amorphous material. (Amorphous metals do not form crystals, which would impede the desired magnetic domains. Non-volatile meant the magnetic fields could retain data without power.)

Dr. Jerry Cuomo, who joined IBM Research in 1963 as a materials scientist, had begun searching for magnetic “bubble domains” in minerals in 1970.

Retired from IBM in 1993, and now Distinguished Professor of Research Materials Science and Engineering at North Carolina State University, Cuomo says the seven-year quest for what became the magneto-optical disk reminds him of the Frank Capra movie, It’s a Wonderful Life. “Everything we do affects other people,” he says. “Looking back, it’s easy to see how the chain of events that led us to the substance and properties we were looking for might have been broken at any point.”

Over the years of trial and error, three critical turning points stand out. First, he says, his research colleague Dick Gambino, who worked in magnetics, suggested combining the rare earth element gadolinium with cobalt. Gambino believed that the molecular structures, or lattices, of the two would complement each other, allowing magnetic domains to “stand upright” or perpendicular—a critical necessity for high-density magnetic recording.

Secondly, Gambino and Cuomo had learned, through advice from an older colleague, the necessity of working with pure samples of materials, such as the gadolinium and cobalt. This would prove critical.

And finally, Dr. Praveen Chaudhari took charge of the function where Cuomo and Gambino worked. Chaudhari would later become director of physical sciences and then vice president of science before leaving IBM to head the US Department of Energy’s Brookhaven National Laboratory.

While attending an offsite conference together, Chaudhari told Gambino he had an idea based on what Cuomo had told him about their results so far. “Why not deposit the combination of gadolinium and cobalt on a substrate that would flex and force the domains to be perpendicular?”

Cuomo used a technique called sputtering to deposit the elements on a substrate. This involved bombarding the metals with energized particles to release atoms, which were then deposited on an adjacent surface, the substrate.

He prepared film deposits on a variety of substrates, including molybdenum. As he walked to the microscope room to examine them for their domain structure, he was interrupted by a colleague. Gambino came along at that moment and examined the samples first. A few moments later, Cuomo heard Gambino yelling, “We got it.”

However, they weren’t there yet. Sputtering the combination of gadolinium and cobalt on a substrate worked—but for the wrong reason. After extensive studies they found the internal forces built into the amorphous material by the sputtering process resulted in the formation of the sought-after perpendicular domains. This wasn’t a commercially viable way to develop high-density magnetic recording material.

Day after day, month after month, the team deposited and carefully examined thousands of samples to gain a fundamental understanding of this new material and its properties. At one point in this long process, the films that were deposited became “contaminated” by the molybdenum holder. Tests made that afternoon in 1972 showed this new, three-component alloy had the superior properties they were looking for. “This new alloy made the technology attractive and competitive,” says Cuomo. They stayed until 4:00 a.m. the next morning, making notes on the potential uses for their discovery.

For the next five years, the three worked on refining their discovery, while beating paths around the world to find an IBM product development lab that needed their new Bubble Memory substance. During this time, however, dramatic improvements in the data capacity and cost of magnetic hard disk drives had made the new Bubble technology commercially unattractive.

But a new problem requiring a new solution was just appearing. By the late 1970s and early 1980s, the amount of data generated by video and multimedia files was creating a need for a new form of high-capacity removable storage. And the most promising technology appeared to be laser-based, optical disks.

After numerous trips to IBM facilities around the world, Cuomo and his colleagues found engineers at the IBM Tucson Development Laboratory in Arizona who had a keen interest in their discovery. In 1991, IBM became the first company to deliver a 3.5-inch rewritable optical drive to the market. And within two years, IBM expanded its product line to include 5.25-inch drive products and optical library storage systems, such as the IBM ® 3995 Optical Library. This machine held an array of optical disks, called cartridges, each initially capable of storing 680 megabytes of data, and eventually eight times that amount, or 5.2 gigabytes.

In 1995, US President Bill Clinton awarded the inventors, Praveen Chaudhari, Jerome J. Cuomo and Richard J. Gambino, the National Medal of Technology—America’s highest honor for technical innovation.


Selected team members who contributed to this Icon of Progress:

  • Praveen Chaudhari IBM scientist and manager of research
  • Jerome J. Cuomo IBM researcher
  • Richard J. Gambino IBM researcher