Ferromagnetic resonance spin pumping in CoFeB with highly resistive non-magnetic electrodes

•We systematically study FMR spin pumping in CoFeB/non-magnet bilayer.•Spin rectification dominates with increasing non-magnetic electrode's resistance.•We firstly observed asymmetric FMR dc voltage from a single CoFeB layer.•We provide a proper analysis method to extract spin Hall angle from FMR spin pumping.•We obtain spin Hall angle of Ta using our proposed method.

The relative contribution of spin pumping and spin rectification from the ferromagnetic resonance of CoFeB/non-magnetic bilayers was investigated as a function of non-magnetic electrode resistance. Samples with highly resistive electrodes of Ta or Ti exhibit a stronger spin rectification signal, which may result in over-(or under-) estimation of the spin Hall angle of the materials, while those with low resistive electrodes of Pt or Pd show the domination of the inverse spin Hall effect from spin pumping. By comparison with samples of single FM layer and an inverted structure, we provide a proper analysis method to extract spin pumping contribution.