Effects of Interface States between Organic Molecules and Ferromagnetic Metals on Organic Molecular Spintronics

Abstract

  Recently, research field of organic molecular spintronics has attracted much attention. One of important issues in this field is to clarify mechanisms of spin injection from ferromagnetic materials into organic molecules. The flatter interface between an organic molecular layer and a ferromagnetic electrode as a spin injector is, the more efficiently spin-polarized carriers are injected. In our study, a planer-type structure that had the flatter interface was adopted. By using electron beam lithography, photolithography and vacuum vapor deposition, Ni₈₀Fe₂₀/tris-(hydroxyquinolinato)-aluminum(Alq₃)/Ni₈₀Fe₂₀ junctions were fabricated and the magnetoresistance (MR) effect was investigated. Devices having shorter distance between Ni₈₀Fe₂₀ electrodes showed the MR effect. Origins of the MR were investigated by the devices with nonmagnetic electrodes, by the devices with tunnel barriers at the interface between the Alq₃ and the Ni₈₀Fe₂₀, and by the devices with another molecule. As the result, it was suggested that the MR was mainly originated from a local magnetic state on the Ni₈₀Fe₂₀ surface.