Novel Magnetic Semiconductor Developed by MIT

Researchers at MIT's Francis Bitter Magnet Lab have developed a novel magnetic semiconductor that may greatly increase the computing power and flexibility of future electronic devices while dramatically reducing their power consumption.

The new material is a significant step forward in the field of spin-based electronics -- or "spintronics" -- where the spin state of electrons is exploited to carry, manipulate and store information. Conventional electronic circuits use only the charge state (current on or off) of an electron, but these tiny particles also have a spin direction (up or down).

The magnetic semiconductor material created by Moodera's team is indium oxide with a small amount of chromium added. It sits on top of a conventional silicon semiconductor, where it injects electrons of a given spin orientation into the semiconductor. The spin-polarized electrons then travel through the semiconductor and are read by a spin detector at the other end of the circuit.

Although the new material is promising in itself, Moodera says the real breakthrough is their demonstration that the material's magnetic behavior depends on defects, or missing atoms (vacancies), in a periodic arrangement of atoms. This cause-and-effect relationship was uncertain before, but Moodera's team was able to tune the material's magnetic behavior over a wide range by controlling defects at the atomic level.

"This is what has been missing all along," he says. "The beauty of it is that our work not only shows this magnetic semiconductor is real, but also technologically very useful."

The new material's ability to inject spin at room temperature and its compatibility with silicon make it particularly useful. Its optical transparency means it also could find applications in solar cells and touch panel circuitry, according to Moodera.

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