Exploring coupling in molecular magnet/qubit bilayers

The molecule-based ferrimagnet (FiM) vanadium tetracyanoethylene (V[TCNE]x, x~2) shows promise in quantum information science and spintronics due to its ultra-low loss magnetic excitations (magnons or spin waves), for example the Gilbert damping constant is typically on the order of 10^-5 at room-temperature. In this work, we deposit V[TCNE]x on top of a thin film of the molecular spin qubit copper phthalocyanine (CuPc) in order to explore spin-magnon coupling. In these bilayers, we observe new peaks in the ferromagnetic/electron paramagnetic resonance (FMR/EPR) spectra. These peaks depend on the orientation of the sample, the magnetization of the FiM, and the applied magnetic field. We explore the mechanisms by which interlayer interactions may give rise to these new resonances with an eye towards potential applications in quantum information.