The research team was able to measure spin transport in a thin film of certain molecules – a material well known in organic light-emitting diodes – at room temperature. They found that this thin molecular film has a spin diffusion length of approximately 62 nm, a length that may have practical applications in the development of spintronics technology. Additionally, while electricity has been used to control spin transport in the past, the thin molecular film used in this study is photoconductive, allowing control of spin transport with visible light.
Information processing devices such as smartphones are becoming more sophisticated because their information recording density is constantly increasing thanks to advances in microfabrication technology. However, in recent years, the physical limits of processing are rapidly approaching, making further miniaturization difficult. However, perhaps the continued need for more sophisticated technology requires a fundamental change in how it works so that faster, smaller new devices can continue to be created.
To meet this demand, a technology called spintronics – using the magnetic spin and charge of electrons – is gaining attention as a key technology that could unlock the next generation of modern electronics. By aligning the direction of the magnetic spin and moving it like an electric current, information can be propagated using very little energy and producing less waste heat.
A research team led by Professors Eiji Shiko and Yoshio Takei from Osaka Metropolitan University’s Graduate School of Engineering has successfully measured spin transport at room temperature in a thin film of alpha-naphthyldiamine derivative (?NPD) molecules, a well-known material in organic light-emitting diodes. This molecular thin film was found to have a spin diffusion length of approximately 62 nanometers, a distance they expect to be usable for practical purposes.
To use spin transport to develop spintronics technology, it is necessary to have a spin diffusion length in the range of tens of nanometers at room temperature for accurate processing. A thin molecular film of ?NPD with a spin diffusion length of 62 nanometers—a long distance for molecular materials—was fabricated for this study by thermal vacuum evaporation. While electricity has been used to control spin transport in the past, this new ?NPD molecular thin film is photoconductive, allowing spin transport to be controlled using visible light.
“For practical use, it will be necessary to reveal more detailed information about the mechanisms of spin injection and spin transport through thin molecular films to control spin transport,” noted Professor Shiko. “Further research is expected to lead to super-energy-efficient devices that consume a small amount of power and have little risk of overheating.”