Efficient spin current generation and suppression of magnetic damping due to fast spin ejection from nonmagnetic metal/indium-tin-oxide interfaces

Abstract

Indium-tin-oxide (ITO), known as transparent electrode material, shows small spin Hall effect. However, by preparing the nonmagnetic metal (NM: Cu or Ag)/ITO interfaces, we observed an efficient charge-spin interconversion due to the Edelstein effect by means of damping modulation and spin pumping measurements. The estimated spin current conductivity for charge-to-spin conversion in NM/ITO interfaces is larger than Pt and β-Ta. Furthermore, the spin-to-charge conversion coefficient λ in Ag/ITO interfaces becomes 0.35 nm, which is comparable with that of the Ag/Bi interface with large Rashba spin splitting. These experimental results imply that a heavy element like Bi is not necessary to realize an efficient spin-charge interconversion at the interface. By the combination of the experimental results of the interconversion effect, we found that the spin ejection time from the interface is as fast as the momentum relaxation time. As a result, we realized not only efficient spin current generation but also suppression of magnetic damping in the contacted ferromagnetic layer. These findings will help us to understand the physics of interfacial charge-spin conversion and provide a new perspective to material research of spin current generator for low-consumption spintronics devices.