Effect of Bi and Ce co-doping in garnet-based materials: Impact on microwave device performance

Microwave devices in the modern era are rapidly integrating new substrates for passive devices such as filters, phase shifters , isolators , and circulators , etc. Garnet ferrites doped with rare-earth elements have emerged as promising candidates for reciprocal and nonreciprocal microwave devices using direction-dependent information transfer. This study demonstrates how Bi and Ce co-doping in yttrium iron garnet enhances microwave device functionality, including operating frequency, phase shift, and isolation. A flip-chip-based FMR configuration with a S-type microstrip line enabled a reciprocal notch filter design with 100 % tunability for 0.4 cerium concentration. The linewidth of the device was observed to be cerium concentration-dependent with a maximum for 0.6. A maximum differential phase shift of approximately 114°/cm was achieved for the Ce = 0.2 sample at an external magnetic field of 6.6 kOe. A straight microstrip line in parallel configuration facilitated nonreciprocal wave propagation in the Bi and Ce co-doped YIG. The nonreciprocal isolation was significantly enhanced with the applied DC bias magnetic field . Experimental results were validated using HFSS simulations, confirming the potential use of substrates made from Bi and Ce co-doped yttrium iron garnet for the fabrication of reciprocal and non-reciprocal microwave devices. • Bi and Ce co-doping in YIG enhances the microwave device functionalities- operating frequency, phase shift, isolation, etc. • There is more than 100 % tunability in a reciprocal notch filter with an applied magnetic field up to 11 kOe. • Filter bandwidth is a distinct function of Ce concentration. • Maximum differential phase shift of 114°/cm was achieved for the Ce = 0.2 sample at an external magnetic field of 6.6 kOe. • Nonreciprocal isolation improves with increasing magnetic field, gives the best results for low Ce concentration samples.