MIT comes with a new way of spinning
A new approach to controlling magnetism in a microchip can open the doors to memory, computation and sensing devices that consume drastically less power than existing versions.
The MIT boffins at Brookhaven National Laboratory have shown that they can control the magnetic properties of a thin film material by applying only a small amount of stress. Changes in magnetic orientation made in this way remain in their new state without the need for any ongoing power, unlike today's standard memory chips, the team has found.
The new discovery that could overcome some of the inherent physical constraints that has slowed progress in this area is reported in the newspaper natural materials. Geoffrey Beach, a professor of Materials Science and Technology and Co-Chair of the MIT Materials Research Laboratory; PhD student Aik Jun Tan; and eight others at MIT and Brookhaven wrote that as silicon microchip approaches the basic physical limits that could attract their ability to continue increasing their potential while reducing their power consumption. Their research has covered a range of new technologies that can come around these limits.
One of the best is an approach called Spintronics, which uses a feature of electrons called spin, instead of its electrical charge. Since spintronic devices can maintain their magnetic properties without the need for constant power, which silicon chips require, they need significantly less power consumption. They also generate much less heat – another major limiting factor for today's devices.
But spintronic technology suffers from its limitations. One of the most significant missing ingredients has been a way to quickly control the magnetic properties of a material electrically by applying a voltage. Many research groups around the world have driven that challenge.
Earlier experiments have called for electron accumulation at the interface between a metal magnet and an insulator, using a device structure similar to a capacitor. The electrical charge can change the magnetic properties of the material, but only with a minimal amount, making it impractical to use in real devices. It has also tried to use ions instead of electrons to change magnetic properties. For example, oxygenations have been used to oxidize a thin layer of magnetic material, causing an extremely large change in magnetic properties. However, the introduction and removal of acid ions causes swelling and shrinkage of the material, causing mechanical damage which limits the process to a few repetitions – making it substantially useful for calculating agents.
The new result shows a way around it, using hydrogen ions instead of the much larger surges used in previous trials. Because the hydrogen ions can zip in and out quickly, the new system is much faster and provides other significant benefits, researchers say.
Because the hydrogen ions are so much smaller, they can come in and out of the crystalline structure of the Spintronican system, change their magnetic orientation each time without damaging the material. The team has now shown that the process does not produce any decomposition of the material after more than 2000 cycles. And unlike oxygenations, hydrogen can easily pass through metal layers, which allows the team to control the properties of layers deep in a device that can not be controlled in any other way.
"When you pump hydrogen to the magnet, magnetization rotates," says Tan, "you can turn the magnetization direction by 90 degrees by applying a voltage – and it's completely reversible." Since the poles of the magnets are oriented to what is used to store information, it means that it is possible to easily write and delete data "bits" in spintronic devices with this effect.