Organic Ferrimagnetic Material Vanadium Tetracyanoethylene for Non-reciprocal Microwave Applications

Vanadium tetracyanoethylene (V(TCNE)2) is an organic ferrimagnetic material known for its ultralow Gilbert damping. Magnetic resonators based on this material demonstrate high Q exceeding 7,000 at ambient, rivaling those of inorganic magnetic materials such as YIG. V(TCNE)2 is of particular interest for non-reciprocal device applications thanks to its micro-patterning capabilities. Here we provide a review of the magnetic and microwave properties of V(TCNE)2 and discuss its application in microwave circulators. Using a generic multimode coupling model, we describe V(TCNE)2-based superconducting circulator and assess its performance in terms of isolation, insertion loss and circulation bandwidth. High isolation (> 59 dB), extremely low insertion loss (< 0.03 dB), and flexible bandwidth control can be potentially realized. By engineering the V(TCNE)2 structures, the devices can operate in both weak and strong coupling regimes, realizing bandwidths from sub-megahertz to hundreds of megahertz. Especially, the narrow-band circulation could benefit noise-sensitive quantum microwave measurements.