Antiferromagnetic materials allow for processing at terahertz speeds

Spellbound fans are glued to the screen. Yes, this could be a goal for the German national team ... Oh no! Just past the post! Selected World Cup games were shown in razor-sharp clarity in ultra high definition (UHD) on domestic TV sets. For most of the time at least. Unfortunately, it is often the case that either the bandwidth of the transmission media cannot keep up with the data flow or the data simply cannot be processed fast enough. Then the picture judders or the high resolution has to be temporarily scaled down, and soccer fans have to make do with lower resolution images.

But very soon such low bandwidths could be a thing of the past. Researchers at the Czech Academy of Sciences together with their colleagues at Mainz University have discovered a way to dramatically increase data processing rates by around one hundred times up to terahertz speeds.

Ferromagnetic and antiferromagnetic memory

In general, data memory and storage rely on the use of ferromagnetic materials. However, these are associated with two drawbacks. Firstly, the areal density and, thus, the storage capacity of these materials is restricted as they necessarily reach natural limits. This is because each bit of information is stored in a kind of tiny bar magnet, each of which represents a 0 or a 1 depending on its alignment. But if these bar magnets are placed too close together, they begin to influence each other. The second problem is that there are also restrictions on the speeds with which data can be written to this type of storage medium. It is not possible to go faster than gigahertz rates. Otherwise it would require immense energy.

But this is not the case with antiferromagnetic memories. They can be written to at a much higher density because in these the bar magnets are always aligned alternately and so have no effect on each other. This means they can store considerably more data. And they allow much faster writing speeds.

Antiferromagnetic memory allows for terahertz processing rates

"If you want to send information, such as moving images of a soccer match, you send this in the form of light that can be transmitted by fiber-optic cables," explained Professor Jairo Sinova, Head of INSPIRE, the Interdisciplinary Spintronics Research group at Johannes Gutenberg University Mainz. "As this is possible at frequencies in the terahertz range, this happens extremely rapidly. At present, the reception speed has to be slowed down to be processed by the computer or television because these devices process and store data using electricity-based techniques, and the speed these operate at is just a few hundred gigahertz. Our antiferromagnetic memory concept is now capable of working directly with data sent at rates in the terahertz range." This means the signal no longer has to be slowed down by the device. Instead it can also be processed at terahertz speeds by the computer or TV.

The team of scientists carried out the initial research back in 2014. They passed an electric current through the antiferromagnets and were thus able to appropriately align the tiny storage units. They originally used a cable for this, a rather slow connection method. "Instead of the cable we use now a short laser pulse to induce an electric current. This current aligns the bar magnets, in other words, their spin moments," said Sinova. Instead of using cables the new memory thus works wirelessly, and instead of requiring direct electric current, the effects are now generated using light. Thanks to this, the researchers were able to dramatically increase speeds, thus meeting the requirements necessary to enable future users to view judder-free, ultra-high definition images.