Researchers at Germany's University of Münster have designed low-loss spin-wave waveguides in yttrium iron garnet thin films using silicon ion implantation, creating an amorphous waveguide cladding. The team's spin waveguide network processes information with far less energy and could offer a promising alternative to power-hungry electronics.
The rapid rise in AI applications has placed increasingly heavy demands on energy infrastructures, causing researchers to look for energy-saving solutions for AI hardware. One promising idea is the use of so-called spin waves to process information. The team in this work, led by physicist Prof. Rudolf Bratschitsch (Münster), has developed a new way to produce waveguides in which the spin waves can propagate particularly far. They have not only created the largest spin waveguide network to date, but also succeeded in specifically controlling the properties of the spin wave transmitted in the waveguide. For example, they were able to precisely alter the wavelength and reflection of the spin wave at a certain interface.
Spin waves have already been used to create individual components, such as logic gates that process binary input signals into binary output signals, or multiplexers that select one of various input signals. Up until now, however, the components were not connected to form a larger circuit. "The fact that larger networks such as those used in electronics have not yet been realized, is partly due to the strong attenuation of the spin waves in the waveguides that connect the individual switching elements - especially if they are narrower than a micrometer and therefore on the nanoscale," explains Rudolf Bratschitsch.
The group used the material with the lowest attenuation currently known: yttrium iron garnet (YIG)., The researchers inscribed individual spin-wave waveguides into a 110 nanometer thin film of this magnetic material using a silicon ion beam and produced a large network with 198 nodes. The new method allows complex structures of high quality to be produced flexibly and reproducibly.
In this work, the team demonstrated low-loss spin-wave waveguides realized by the implantation of silicon ions in a thin YIG film. They verified spin-wave decay lengths exceeding 100 µm and tailored dispersion tuning. Using the new spin-wave waveguide technology, they demonstrated a spin-wave network with 198 crossings. The maskless implantation process allows for the fabrication of multiple tailored spin-wave structures on a single substrate and can be scaled up to create wafer-size magnonic integrated circuits.