Electronic Design

Spin the Electron

Jagadeesh Moodera's world is spinning. That's because the senior research scientist and his team at the Massachusetts Institute of Technology are using spin-oriented electrons to create a new type of magnetic semiconductor. The device promises to increase the power and flexibility of future electronic devices while dramatically reducing energy consumption.

Moodera's invention is based on spintronics. The emerging technology uses electron spin orientation to carry, manipulate and store information, literally adding a new dimension to electronic circuits. One type of spintronic sensor is already used on the magnetic platters of compact, high-capacity miniature hard drives, the kind found in iPods and similar products. Moodera, who works in MIT's Francis Bitter Magnet Lab, hopes to extend the concept into electronic circuits.

Conventional electronics relies on on/off current states to convey information. By increasing the number of states, spintronics will multiply the amount of information circuits can transmit. "We can carry information in two ways at once, and this will allow us to further reduce the size of electronic circuits," he says.

The key to Moodera's research is indium oxide, to which Moodera and his research team added a dash of chromium. The material sits on top of a regular silicon semiconductor, injecting a stream of spin-oriented electrons into the device. The oriented electrons travel through the semiconductor and are read by a spin detector positioned at the end of the circuit.

The material's magnetic behavior depends on missing oxygen atoms, known as "vacancies," that create gaps in a periodic arrangement of atoms. By controlling the defects at an atomic level, Moodera and his team are able to tune the material's behavior over a wide range. "Our new material is one of the strong candidates for spin injection into conventional semiconductors," says Moodera. "It allows one to manipulate the spins on nanoscale devices for information storage and processing." Moodera sees a spin field effect transistor (SpinFET), as a likely outcome of his research. "That is the building block of microprocessors in electronic devices," he says.

By allowing designers to cram more features into smaller form factors, spintronic circuits could lead to a new generation of smaller and more versatile electronic systems and products. Improved energy efficiency is another potential benefit. Since spin states are non-volatile, information can be stored in a circuit without the need for a continuous charge. Spin information can also be sent without moving charges. "It's like creating ripples in a pond, says Moodera, "It travels all the way across without adding more energy."

But engineers won't be adding spin semiconductors to their design toolsets anytime soon. "There is plenty more research to be done," says Moodera. He notes that it took conventional semiconductor technology decades to advance from the lab into commercial microprocessors. "Let us hope that it does not take us that long," says Moodera. "We are confident that it will happen a lot sooner than that."

Massachusetts Institute of Technology

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