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New Technique Uses Organic Molecules to Fabricate Novel Spintronic Devices

Physicists have developed a new technique for the fabrication of unique types of electronic components called spintronic devices. Since the future of such low-power, high-performance devices looks promising, efficient means to develop them are highly in demand.

A diagram to show the composition of the experimental samples used in the study. (Image credit: © 2019 Isshiki et al.)

The new fabrication technique is intriguing since it employs organic molecules that are comparatively easy to configure for various purposes. Several layers of molecules could be printed or painted onto metals to develop new electronic functions.

Put simply, someday, spintronic devices could replace a number of electronic devices because spintronics is a more efficient method for carrying out certain functions that electronics can perform currently.

While electronic devices rely on the flow of charge in the form of electrons in motion, spintronic devices use a distinct property of electrons called spin. This is related to the angular momentum of the electron and the flow of spin is known as spin current.

A number of difficulties arise while attempting to achieve useful spintronic devices, such as finding ways to induce a spin current and, once this is realized, to instill spintronic components with beneficial functions, for example, the potential to retain data for use as high-speed memory.

Research Associate Hironari Isshiki and his colleagues from the University of Tokyo’s Institute for Solid State Physics have discovered an innovative and elegantly simple method to overcome both of these difficult 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.

Hironari Isshiki, Research Associate, University of Tokyo

Isshiki continued, “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 formed of a substance known as lead(II) phthalocyanine. Upon injecting a spin current into the surface covered by the molecule, it is effectively transformed into a familiar charge current.

The scientists performed experiments with layers of varying thicknesses to identify which would be most effective. The molecules in the layer with a thickness of a single molecule aligned into a uniform arrangement, yielding 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.

Isshiki added, “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 future steps for Isshiki and his team are to investigate other configurations of organic layers on conductive materials to achieve innovative spin functionalities. The team also intends to analyze the conversion of charge into spin current, the reverse process to the one discussed in this study. The aim of this field of research is to considerably speed up the study of spintronics using organic molecules.


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