Extremely Large Magnetization and Gilbert Damping Modulation in NiFe/GeBi Bilayers

We have fabricated NiFe/GeBi heterostructures and investigated the spin pumping effect. The GeBi semiconductor film had a remarkable impact on the magnetization of the GeBi/NiFe structure, which may have been caused by the strong spin–orbit coupling of the Bi ions that can affect the torque orientation of NiFe. When a nanometer thick Cu film was inserted in the film structure (GeBi/Cu/NiFe), the coercive force of the new film decreased, and the saturation magnetization increased, because Cu isolated the coupling between the GeBi and NiFe layers. Ferromagnetic resonance (FMR) measurements showed that the GeBi/Cu/NiFe heterostructure had a reduced Gilbert damping and resonance field HFMR, when compared with those of the GeBi/NiFe thin film. This work indicated that the GeBi could be used for adjusting both the magnetization and Gilbert damping constant dramatically.