Spintronics 'Miracle Material' Put to the Test


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Two Spintronic Devices

wavelength.jpgThe next step, which Vardeny and Wang accomplished in their recent work, was to incorporate hybrid perovskite into spintronic devices. The first device is a spintronic light-emitting diode, or LED. The semiconductor in a traditional LED contains electrons and holes—places in atoms where electrons should be, but aren’t. When electrons flow through the diode, they fill the holes and emit light.

Wang says that a spintronic LED works much the same way, but with a magnetic electrode, and with electron holes polarized to accommodate electrons of a certain spin.  The LED lit up with circularly polarized electroluminescence, Wang says, showing that the magnetic electrode successfully transferred spin-polarized electrons into the material.

“It’s not self-evident that if you put a semiconductor and a ferromagnet together you get a spin injection,” Vardeny adds. “You have to prove it. And they proved it.”

The second device is a spin valve. Similar devices already exist and are used in devices such as computer hard drives. In a spin valve, an external magnetic field flips the polarity of magnetic materials in the valve between an open, low-resistance state and a closed, high-resistance state.

Wang and Vardeny’s spin valve does more. With hybrid perovskite as the device material, the researchers can inject spin into the device and then cause the spin to precess, or wobble, within the device using magnetic manipulation.

That’s a big deal, the researchers say. “You can develop spintronics that are not only useful for recording information and data storage, but also calculation,” Wang says. “That was an initial goal for the people who started the field of spintronics, and that’s what we are still working on.”

Taken together, these experiments show that perovskite works as a spintronic semiconductor. The ultimate goal of a spin-based transistor is still several steps away, but this study lays important groundwork for the path ahead.

“What we’ve done is to prove that what people thought was possible with perovskite actually happens,” Vardeny says. “That’s a big step.”

This work was funded by the U.S. Department of Energy Office of Science.

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