26 August 2013

Magnetic Mystery Behind Lanthanum Aluminate and Strontium Titanate Combine Computer Processors with Memory Chips

Scientists have theorized how two non-conductive and non-magnetic materials, Lanthanum Aluminate and Strontium Titanate, become conductive and magnetic when combined together. This phenomenon can lead to the development of computer memory with data processing capabilities.

Scientist believe that because of a magnetic phenomenon called "local moments", lanthanum aluminate and strontium titanate, become conductive and magnetic when placed together. With these two properties, these two semiconductors have the ability to process binary data (like a computer processor) and also have the ability to store them (like a memory chip) in one device; a computer processor that can store data.

A semiconductor is a material that has conductive properties midway between a conductor like metal and a non-conductor such as glass. Because of this, depending on the flow of electrons in the semiconductor, it can be either on (1) where electrons can flow freely or off (0) when electrons cannot pass through. Data that is streamed through these semiconductors can be permanently stored on magnetic devices.

Local Moments Lead To Next Gen Chips

They're not exactly the peanut butter and jelly of semiconductors, but when you put them together, something magical happens.

Alone, neither lanthanum aluminate nor strontium titanate exhibit any particularly notable properties. But when they are layered together, they become not only conductive, but also magnetic.

In the current online edition of Nature Physics, researchers at The Ohio State University report the first-ever theoretical explanation to be offered for this phenomenon since it was discovered in 2004.

Understanding how these two semiconductors interact at their interface could someday lead to a different kind of material—one that provides a single platform for computation and data storage, said Mohit Randeria, co-author of the paper and professor of physics at Ohio State.

Video: What is a semiconductor?

"The whole question is, how can you take two materials which do not conduct electricity and do not have magnetic properties, make a sandwich out of them and—lo and behold—at the interface tween them, charge begins to flow and interesting magnetic effects happen?" he said.

"It's like taking two pieces of bread and putting them together and having the sandwich filling magically appear."

By making calculations and modeling the basic physical properties of both materials, Randeria's team has hit upon an explanation for the behavior that seems ironic: the interface between two non-magnetic materials exhibits magnetism.

The team showed how the elemental units of magnetism, called "local moments," are formed at the interface of the two materials. They then showed how these moments interact with the conducting electrons to give rise to a magnetic state in which the moments are arranged in an unusual spiral pattern.

If the physicists' explanation is correct, then perhaps someday, electronic devices could be constructed that exploit the interface between two oxides. Theoretically, such devices would combine the computational abilities of a silicon chip with the magnetic data storage abilities of permanent magnets like iron.

"If you had conduction and magnetism available in the same platform, it could be possible to integrate computer memory with data processing. Maybe different kinds of computation would be possible," Randeria said.

But those applications are a long way off. Right now, the physicists hope that their theoretical explanation for the strange magnetic behavior will enable other researchers to perform experiments and confirm it.

Randeria's coauthors included Ohio State postdoctoral researcher Sumilan Banerjee and former doctoral student Onur Erten, who graduated this summer and is about to begin a postdoctoral fellowship at Rutgers, The State University of New Jersey.


Ohio State University
Nature Physics
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