FeriMag · Ferrite heterostructures for integrated magnonics

I aim to develop a novel material system with intrinsically nonreciprocal spin-wave dispersion relation, based on ferrimagnetic insulator bilayers. Nonreciprocity is a crucial property in signal processing, as it can be used to design e.g. circulators - devices that allow to use the same antenna for receiving and transmitting signals. Current technology uses bulk ferrite materials and permanent magnets to achieve this behavior. However, this makes the circulators too big for applications in personal devices such as mobile phones or smart watches. For this reason, the current technology uses different frequencies for transmitted and received signal, effectively halving usable bandwidth. Strong nonreciprocity has been achieved in synthetic antiferromagnets made of metallic bilayers, relying on the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction to stabilize the noncolinear configuration. However, the high attenuation in these layers prevents any real industrial application. On the other hand, the lack of easily accessible RKKY interaction in low-damping magnetic insulators, such as yttrium-iron-garnet (YIG), makes it difficult to achieve nonreciprocal properties in these materials. My idea is to overcome this lack of RKKY interaction in YIG by stabilizing the noncolinear magnetic configuration by altering the direction of the magnetic anisotropy separately in each layer. Such a material system can be exploited to design multifunctional devices integrated on micrometer-sized chips for mmWave in 5G and future 6G technologies. These devices can be subsequently utilized in e.g., autonomous vehicles, smart cities, and thus help to overcome challenges connected to dense communication networks.