Multifunctional Oxide Heterostructures For Next-Generation Tunable RF/Microwave Electronics

Recent advanced radio frequency (RF) microwave device demands for low power consumption, light weight, compact package, and high performance. To achieve the high performance, applying magnetic materials is becoming indispensable in many of those devices. Thus, the role of magnetism in those devices is important high-quality magnetic materials not only improves the performance of microwave devices but also opens opportunities in developing novel concepts of devices utilizing spin wave excitation, non-reciprocal wave propagation, and the electromagnetic coupling in multiferroic materials. Among all the others, manipulating magnetic properties in multiferroic material started a couple years ago. Multiferroic materials are a group of materials that exhibit both ferrimagnetic and ferroelectric properties. By controlling its magnetic property such as ferromagnetic resonance, the low loss and tunable RF/Microwave electronics can be generated. However, the multiferroics currently under investigation suffer severely from the weak magnetoelastic effect in part due to the poor crystallinity, and in part due to the inappropriate materials chosen. Thus, the fabrication of high-quality ferrite and discovery of the suitable ferrite are paramount to apply in multiferroic material. In this research, we report a high-quality Yttrium Iron Garnet thin film and an unique Aluminum alloyed Nickel Zink Ferrite thin film. The former exhibits an extremely low magnetic damping factor, and the later show a larger magnetostriction coefficient. The microstructures of these films were characterized using X-ray diffraction, Atomic force microscopy, and transmission electron microscope. and - the magnetic properties -were characterized by Ferromagnetic Resonance. Additionally, we have observed the inverse spin-hall effect between magnetic and metal layer and demonstrated non-reciprocal wave propagation in a 20nm thin YIG film.