Magnon Engineering in Vanadium Tetracyanoethylene

The low-loss ferrimagnet vanadium tetracyanoethylene (V[TCNE]_x, x~2) has shown promise in quantum information science and spintronics due to its ultra-low loss magnetic excitations (magnons or spin waves), with Gilbert damping typically in the range of 4x10^-5 at room-temperature. In this work, we expand our control over V[TCNE]_x magnetization dynamics by creating V[TCNE]_x/V[TCNE]_x bilayers by depositing V[TCNE]_x on a molecular seed layer (e.g., copper phthalocyanine, CuPc) and by varying growth conditions. We observe multiple magnetic phases and indications of strain relaxation that modify the low temperature (T = 5K) static and dynamic magnetic properties. These studies open new avenues for control of magnon properties with relevance for designing microwave-magnon and spin-magnon quantum devices.