Spintronics and optronics, better together

In research conducted for the EU Spice project, Spintec demonstrated an optical magnetic tunnel junction that is 1,000 times faster than magnetic tunnel junctions that use an electric write current. This breakthrough could lead to non-volatile MRAM with unprecedented levels of performance.

Earlier in this project, Spintec had shown that a femtosecond laser could effectively reverse the magnetization of a termium cobalt layer. Here, the gap with an electrical current—which maxes out at around 100 picoseconds—was already substantial. At this stage, however, the demonstration was on the material, not on a functional MTJ.

The path toward memory points of 30 nm and possibly even 20 nm

The researchers recently reached this milestone, by replacing the MTJ’s top metal contact (usually aluminum and tantalum) with a transparent material the laser light could pass through. They settled on indium tin oxide, widely used in LCD displays. Memory points measuring 80 nm in diameter were fabricated using standard deposition and etching processes.  Ultimately, the researchers hope to come down to 30 nm, and possibly even 20 nm.

MRAM memory could benefit from smaller MTJs that enable faster write speeds while consuming less energy due to the use of the energy-efficient laser. Only the read phase would remain electrical, at least in the near term. This will ensure that each memory point can be read individually. The laser wavelength of 800 nm cannot be focused on MTJs this small in diameter.

Contact: ricardo.sousa@cea.fr

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