Spin current switch demonstrated

“This is significant because although the technology behind detecting and generating the spin current has been established for some time, a long-missing component in the history of spintronics has been a spin current switch,” said Tohoku University, equating it to a transistor in charge-based electronics.

The device has a three layer structure, which sandwiches a chrome oxide (Cr₂O₃) layer between yttrium iron garnet (YIG) and platinum (Pt).

The YIG/Pt pair is a standard combination of materials used to investigate the current flow – both are insulators, blocking electron flow.

YIG, a ferrimagnet electric insulator, generates spin current in response to microwaves (spin pumping) or temperature gradient (spin Seebeck effect) and Pt, a paramagnetic metal, detects the spin current as an electric voltage via the inverse spin hall effect (ISHE) – which changes spin current from elsewhere into electrical voltage.

With the Cr₂O₃ layer included, the voltage signal at the Pt reflects how the Cr₂O₃ layer transmit the current, allowing changes against temperature and applied magnetic field to be identified.

“We observed a massive reduction in the voltage signal when crossing the temperature at around 300K, at which point Cr₂O₃ changes its phase from paramagnet to anti-ferromagnet [the Neel point],” said researcher Dazhi Hou. The change of the spin current transmission is close to 5x when a magnetic field is applied – suggesting that the layered structure works as a spin current switch when crossing the Neel point of Cr₂O₃ or applying a magnetic field.

The work is described in the Nature Materials paper ‘Spin colossal magnetoresistance in an antiferromagnetic insulator‘.

Diagram: Illustration of the out-of-plane spin Seebeck setup for the YIG/Cr₂O₃/Pt trilayer device.

Photo: TEM image of the YIG/Cr₂O₃/Pt trilayer device – scale bar is 5nm

Both images taken from Tohoku University website, which requested they be credited to Nature Publishing Group.