Organic Ferrimagnetic Material Vanadium Tetracyanoethylene for Non-reciprocal Microwave Applications

Vanadium tetracyanoethylene ($V$(TCNE)2) is a new organic ferrimagnetic material known for its ultra low Gilbert damping. Magnetic resonators based on this material demonstrate high quality factors exceeding 7,000 at ambient conditions, rivaling those of inorganic magnetic materials such as Yttrium Iron Garnet (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 potential applications in microwave circulators. Using a generic multimode coupling model, we describe $V$(TCNE)2-based superconducting circulator and assess its optimal 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 various circulation bandwidths from sub-megahertz to hundreds of megahertz. Especially, the narrow-band circulation could serve as a filter function and benefit noise-sensitive quantum microwave measurements.