ICP酸化法による強磁性トンネル接合の作製  [in Japanese] Fabrication of Ferromagnetic Tunnel Junctions with ICP Oxidized Tunnel Barriers  [in Japanese]

Ferromagnetic tunnel junctions with a spin-valve-like structure of NiFe/Co/Al-O/Co/IrMn were fabricated by inductively coupled plasma-assisted magnetron sputtering using metal masks. The tunnel barriers were formed by oxidization of an Al layer using an inductively coupled oxygen-argon mixed plasma. The dependence of the saturated resistance (R_s), magnetoresistance (MR) ratio, barrier height (φ), and width (d) on the oxidization time and Al thickness were investigated. R_s increased linearly and the MR ratio increased rapidly with increasing oxidization time. The MR ratio saturated when the oxidization time exceeded 120sec. When the Al thickness was decreased from 1 to 0.5 nm, the MR ratio and φ decreased, while d increased. Below 1nm, the Al layer was not continuous, but an island-like structure.