Ferromagnetic Electrodes Used in New Electronic Memory Switch

The innovation could lead to faster memories and computers

By on February 22nd, 2012 08:24 GMT

A group of investigators from the US National Institute of Standards and Technology (NIST) highlights the development of a new type of electronic switching mechanisms. They say that the device could lead to significant improvements in memory capabilities, and also to faster processing.

Novel computer memory systems rely on layered switching devices in order to function properly. However, these devices are also one of the main limitations that now stand between advanced memories and widespread use.

What experts are trying to do is create faster, lower-powered computers. In order for a processor to work faster and more efficiently, it needs full access to fast memory systems. Switching mechanisms are the gatekeepers, as it were, so their performances place limits on the entire computer.

One of the main directions for research nowadays is the creation of nonvolatile memories, of the type that retain the information they were carrying even when the power is turned off. In practical terms, this would translate into a laptop resuming the operations from where it left off, once turned on again.

Obviously, this type of memories already exists, but NIST scientists wanted to improve on the design. Usually, switches that have the ability to retain data are made up of transition-metal oxides. One particular type of nonvolatile memory is made up of four layers of materials.

Two metal layers that play the role of electrodes are placed on either side of a copper layer and a metal oxide layer. The resulting structure is (metal layer)-(copper layer)-(metal oxide layer)-(metal layer). Whenever a voltage is passed from one electrode to the other, the system acts like an on/off switch.

Researchers want to be able to use such switches in working memories attached directly to microprocessors. However, the current technology does not allow for the necessary level of performances. The NIST team built its own version of the switching mechanism in the new study.

Rather than using nonmagnetic metals for creating the two electrodes, the team used ferromagnetic metals. When an electrical current passes through these electrodes, tiny filaments stretch out from the copper layer located between them, permeating the metal-oxide layer for distances up to 16 nanometers.

“The presence of such filaments is the only explanation that makes any sense as to why our structures make such good switches,” NIST Semiconductor Electronics Division expert Curt Richter explains.

“Only if a filament made of high-quality copper formed would the spins maintain their state. This finding was an end in itself, but it also suggests the layered structure could have applications in ‘spintronics’ where electron spin is used to carry and process information,” he concludes.
This image shows a copper filament forming between two electrodes of the same magnetic orientation (top and bottom layers). The copper layer is orange, and the metal (tantalum) oxide layer is blue.
   This image shows a copper filament forming between two electrodes of the same magnetic orientation (top and bottom layers). The copper layer is orange, and the metal (tantalum) oxide layer is blue.
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