Researchers Use Atom-Thin Insulator to Transport Spins Without Any Losses

An intermediate layer containing a few atoms is serving to enhance the transfer of spin currents from one material to the next. Thus far, this process has involved substantial losses.

Researchers from Martin Luther University Halle-Wittenberg (MLU), the Freie Universität Berlin, and the Max Planck Institute (MPI) for Microstructure Physics, explain in the scientific journal "ACS Nano Letters" how this can be prevented.

The scientists thus reveal key new insights pertinent for numerous spintronic applications, for example, futuristic ultra-fast and energy-efficient storage technologies.

In advanced microelectronics, the charge of electrons is used to transport information in mobile phones, electronic parts and storage media. The charge transport necessitates a comparatively large amount of energy and produces heat.

Spintronics could deliver an energy-efficient alternative. The general idea is to exploit spin in information processing. Spin can be defined as the intrinsic angular momentum of the electrons that produces a magnetic moment. This produces the magnetism that will eventually be employed to process information.

In spintronics, spin currents also need to be transported from one material to the next.

In many cases, the spin transport across interfaces is a very lossy process.

Professor Georg Woltersdorf, Study Lead and Physicist, Martin Luther University Halle-Wittenberg

The researchers sought a way to alleviate these losses by using a method that, at first, sounds rather conflicting: they added an insulating barrier between the two materials.

We designed the insulator at the atomic level so that it turned metallic and could conduct the spin currents. This enabled us to significantly improve the spin transport and optimise the interfacial properties.

Professor Georg Woltersdorf, Study Lead and Physicist, Martin Luther University Halle-Wittenberg

The material samples were made at the MPI for Microstructure Physics. The unanticipated effect was discovered via measurements of spin transport carried out at MLU and the Freie Universität Berlin. The researchers also provide the theoretical foundation for the new discovery. According to Woltersdorf, this can be illustrated using comparatively simple models without spin-orbit coupling.

The results are very pertinent for numerous spintronic applications. For example, they can be employed to enhance spintronic terahertz emitters. Terahertz radiation is applied in research as well as in medicine, high-frequency electronics, communication technology, and materials testing.

The study received funding from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) and the European Union.

Journal Reference:

Wahada, M. A., et al. (2022) Atomic Scale Control of Spin Current Transmission at Interfaces. ACS Nano Letters. doi.org/10.1021/acs.nanolett.1c04358.