デュアルスピンバルブタイプ強磁性二重トンネル接合の熱処理による特性変化

概要

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Exchange-biased dual spin-valve type magnetic double tunnel junctions (DSV-MTJs) of Ir-Mn/Co-Fe/AlO_x/Co-Fe/AlO_x/Co-Fe/Ir-Mn were annealed at 175-400℃. After annealing at 325℃, the magnetoresistance (MR) ratio and bias voltage V_h, at which the MR ratio is reduced by 50%, in the DSV-MTJs were greatly increased to 42% and 930 mV, respectively. After annealing above 325℃, the MR ratio and V_h decreased. This degradation of DSV-MTJs annealed above 325℃ was investigated using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The XPS spectra and TEM images showed that an AlO_x/MnO_x composite tunnel barrier was formed due to the diffusion of Mn through the Co-Fe layer and oxygen redistribution above 300℃. Taking into account the spin-independent two-step tunneling via defect states in the barrier, we considered that this AlO_x/MnO_x composite barrier leads to decreasing the MR ratio and V_h and increasing the tunnel resistance.
社団法人日本磁気学会の論文
2001-04-15