Spin devices get a paint job

September 12, 2019

Physicists created a new way to fabricate special kinds of electronic components known as spintronic devices. These high-performance, low-power devices have a promising future, so efficient ways to make them are highly sought after. The new fabrication method is interesting because it uses organic molecules which are relatively easy to configure for different purposes. Layers of molecules could be painted or printed onto metals to create new electronic functions.

In a nutshell, spintronic devices may one day supersede many electronic devices. This is because spintronics is a more efficient way to perform some functions that electronics can at present. Whereas electronic devices depend on a flow of charge in the form of electrons in motion, spintronic devices exploit a different property of electrons known as spin. This is related to the electron's angular momentum and the flow of spin is called a spin current.

There are several challenges to realize useful spintronic devices. Among these are to find ways to induce a spin current and once that's achieved, to imbue spintronic components with useful functions such as the ability to retain data for use as high-speed memory. Research Associate Hironari Isshiki and his team from the University of Tokyo's Institute for Solid State Physics have found a novel and elegantly simple way to tackle both of these complex challenges.

"We successfully demonstrated an efficient conversion of spin current to charge current in a copper sample thanks to a simple coat of 'paint.' This layer is only one molecule thick and comprises an organic substance," said Isshiki. "The device's conversion efficiency is comparable to that of devices made with inorganic metallic materials such as platinum or bismuth. However, in comparison to the inorganic materials, organic materials are much easier to manipulate in order to produce different functionality."

This organic layer is made of a substance called lead(II) phthalocyanine. A spin current injected into the surface covered by the molecule is efficiently converted to a familiar charge current. The researchers experimented with layers of different thickness to see which would be most effective. When the layer was a single molecule thick, the molecules aligned into an ordered arrangement which yielded the most efficient spin to charge current conversion.

"Organic molecules in particular offer spintronic researchers a high degree of design freedom as they are relatively easy to work with. The kinds of functional components we hope to see are things that could be useful in the field of high-performance computing or in low-power devices," explained Isshiki. "The incredibly thin layers required also mean we might one day create flexible devices or even devices you could create with a special kind of printer."

The next steps for Isshiki and colleagues are to explore other configurations of organic layers on conductive materials to realize novel spin functionalities. They also wish to investigate conversion of charge into spin current, the reverse process to that seen in this demonstration. This area of research aims to greatly accelerate the study of spintronics with organic molecules.
Journal article

Hironari Isshiki, K. Kondou, Sei Takizawa, Koki Shimose, Takeshi Kawabe, Emi Minamitani, Naoya Yamaguchi, Fumiyuki Ishii, Akitoshi Shiotari, Yoshiaki Sugimoto, Shinji Miwa, and Yoshichika Otani. Realization of spin dependent functionality by covering a metal surface with a single layer of molecules. Nano Letters. DOI: 10.1021/acs.nanolett.9b02619

This research is supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan under grants JP26103002, JP17H05180, JP17K14077, JP18H03880, JP26102017, JP18H04481, JP15H03561 and JP17H05215.

Otani Laboratory https://www.issp.u-tokyo.ac.jp/maincontents/organization/labs/otani_group_en.html

Institute for Solid State Physics http://www.issp.u-tokyo.ac.jp/index_en.html

Research Contact

Professor Yoshichika Otani
Institute for Solid State Physics, The University of Tokyo
5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 JAPAN
Tel: +81-4-7136-3507 Email: yotanil@issp.u-tokyo.ac.jp

Research Associate Hironari Isshiki
Institute for Solid State Physics, The University of Tokyo
5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 JAPAN
Tel: +81-4-7136-3507 Email: h_isshiki@issp.u-tokyo.ac.jp

Press Contacts

Ms. Madoka Mochida
Institute for Solid State Physics, The University of Tokyo
5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 JAPAN
Email: press@issp.u-tokyo.ac.jp

Mr. Rohan Mehra
Division for Strategic Public Relations, The University of Tokyo
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, JAPAN
Tel: +81-3-5841-0876 Email: press-releases.adm@gs.mail.u-tokyo.ac.jp

About the University of Tokyo

The University of Tokyo is Japan's leading university and one of the world's top research universities. The vast research output of some 6,000 researchers is published in the world's top journals across the arts and sciences. Our vibrant student body of around 15,000 undergraduate and 15,000 graduate students includes over 4,000 international students. Find out more at https://www.u-tokyo.ac.jp/en/ or follow us on Twitter at @UTokyo_News_en.

University of Tokyo

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