Title: Detection of spin pumping free of rectification and thermal artefacts in molecular-based ferromagnetic insulator V[TCNE]x~2

Abstract: The molecular-based ferrimagnetic insulator V(TCNE)x has gained recent interest for efficient spin-wave excitation due to its low Gilbert damping ratio a=4E-5, and narrow ferromagnetic resonance linewidth f=1Oe. Here we report a clean spin pumping signal detected on V(TCNE)x/metal bilayer structures, free from spin rectification or thermal artifacts. On-chip coupling of microwave power is achieved via a coplanar waveguide to measure the in-plane angle-dependence of the inverse spin-Hall effect under ferromagnetic resonance conditions with respect to a constant external magnetic field. A signature of pure spin current from V(TCNE)x is observed in both platinum and permalloy metal layers, demonstrating the utility of V(TCNE)x for magnon spintronics studies in molecule/solid-state heterostructures.