強磁性トンネル接合の磁場中熱処理効果

概要

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The annealing effect of ferromagnetic tunnel junctions was studied so as to achieve a higher MR ratio for the junction of an NiFe / Co_xFe_<1-x> / Al-O / Co_xFe_<1-x> / IrMn system.We fabricated NiFe / Co_<90>Fe_<10> / Al-O / Co_<90>Fe_<10> / IrMn junctions (sample 1) using metal masks. R_s increased monotonically with increasing annealing temperature. The MR ratio increased up to 300°C and rapidly decreased as a result of annealing at higher temperatures. The barrier height (φ) increased and the barrier width (d) decreased with increasing annealing temperature. It is thought that a suitable Al-O barrier was formed by annealing and that the MR ratio increased as a result. To obtain more date, we measured the saturated magnetization (M_s).M_s decreased rapidly as a result of annealing over 300°C : this corresponds to the rapid decrease in the MR ratio.Next, we fabricated NiFe / Co_<75>Fe_<25> / Al-O / Co_<75>Fe_<25> / IrMn junctions (sample 2) without breaking the vacuum in the stacking process.The maximum MR ratio was 49% after annealing at 200°C. The annealing temperature dependence of samples 1 and 2 were quite different.
社団法人日本磁気学会の論文
2000-04-01