Seagate used heat-assisted magnetic recording (HAMR) as it becomes the first hard drive maker to achieve a density of one terabit (one trillion bits) per square inch on a disk drive platter.

The HAMR technology used to achieve the benchmark, which Seagate said it would introduce in products later this decade, will also lead to the production of 3.5-inch hard drives with up to 60TB of capacity.

Seagate patented HAMR in 2006 to lay the foundations for reaching the areal density milestone.

At the most basic level, HAMR uses nanotube-based lubrication to allow the read/write head of a disk drive to get closer to the surface of a spinning platter in order to store more data.

Using HAMR technology, Seagate achieved a linear bit density of about two million bits per inch, resulting in a data density of just over one trillion bits, or one terabit, per square inch - 55% higher than today's areal density ceiling of 620 gigabits per square inch.

"Hard disk drive innovations like HAMR will be a key enabler of the development of even more data-intense applications in the future, extending the ways businesses and consumers worldwide use, manage and store digital content," said Mark Re, senior vice president of Heads and Media Research and Development at Seagate.

With an areal density of 620 gigabits per square inch, today's 3.5in hard drives have a maximum capacity of 3TB. Laptop drives, or 2.5in drives, top out at 750GB or roughly 500 gigabits per square inch.

The first generation of HAMR drives, at just over one terabit per square inch, will likely more than double the latter capacities - to 6TB for 3.5in drives and 2TB for 2.5in models.

HAMR has a theoretical areal density limit ranging from 5-10 terabits per square inch, enough to enable 30TB to 60TB 3.5in drives and 10TB to 20TB for 2.5in drives.

Prior to HAMR, the most significant breakthrough in drive density was perpendicular magnetic recording (PMR), which Seagate and Hitachi use in their drives today. That technology was introduced in 2006 and is also used in magnetic tape cartridge production. PMR basically stood bits upright on a platter's surface so they could be packed closer together.

PMR technology is also expected to allow companies to reach the one terabyte per square inch milestone in the next few years, but that will also mark the technology's upper limits, Seagate said.

For an analogy of how densely HAMR technology can pack data bits together, Seagate looked to the Milky Way, saying the technology can already store more bits per square inch than there are stars in the galaxy. It's estimated there are as many as 400 billion stars in the Milky Way.

Just as PMR had its challenges with overcoming disruptions caused by bit magnetisation years ago, HAMR technology also faces significant hurdles. As drive manufacturers pack more bits per square inch on the surface of a disk platter, they also tighten the data tracks, the concentric circles on the disk's surface that anchor the bits. The challenge as those tracks tighten is overcoming magnetic disruption between the bits of data, which causes the superparamagnetic effect, causing bits to flip their magnetic poles resulting in data errors.