Abnormal spin-pumping effect at Pt/NiFe interface by an oxidation of ferromagnet

• The ISHE voltage is measured in Pt/[nonoxidized or oxidized NiFe] samples.
• The ISHE voltage from the Pt/oxidized NiFe is significantly decreased.
• The spin-pumping effect is suppressed by the oxidation of Pt/NiFe interface.
• The well-defined Pt/NiFe interface is demonstrated to be a reasonable spin-pumping.

The Inverse Spin Hall Effect (ISHE) voltage induced by spin-pumping was measured in Pt/[nonoxidized or oxidized NiFe] samples. The spectrum shape of the DC voltage signal was well-reproduced by simple Lorentzian functions, which were consistent with the prediction of ISHE in Pt/nonoxidized NiFe sample. On the other hand, the voltage signal from the Pt/oxidized NiFe was significantly decreased in accordance with abnormal ferromagnetic resonance (FMR) behavior. The origin of the ISHE voltage degradation was investigated by the FMR spectrum and X-ray photoelectron spectroscopy (XPS) analyses. The spin-pumping was suppressed by the oxidation of NiFe layer and deficient Pt/NiFe interface. The well-defined ferromagnet and clear interface with a normal spin mixing conductance were experimentally demonstrated to be reasonable spin-pumping.