Tunnel magnetoresistance in the ultrathin MnGa-based perpendicular MTJs with bcc-Co based interlayers

bcc-Co系中間層を用いたMnGa-垂直磁化トンネル磁気抵抗素子のトンネル磁気抵抗効果

鈴木 和也; 一ノ瀬 智弘*; 飯浜 聡*; 門馬 簾*; 鎌田 尚樹*; 水上 成美*

Suzuki, Kazuya; Ichinose, Tomohiro*; Iihama, Satoshi*; Momma, Ren*; Kamata, Naoki*; Mizukami, Shigemi*

垂直磁気トンネル接合(p-MTJ)は、磁気抵抗ランダムアクセスメモリ,磁気センサー,高周波デバイスなどの豊富なアプリケーションのためのキーデバイスである。用途に応じた適切な磁気特性が求められるだけでなく、動作温度における高いTMR比も必要とされる。正方晶Mn系合金は、飽和磁化が小さく、保磁力が大きく、垂直磁気異方性が大きく、ギルバート減衰係数が小さいため、p-MTJの電極材料として魅力的な垂直磁化材料の一つである。しかし、Mn系合金を強磁性電極として用いたp-MTJでは、FeCo間層を用いても室温で最大60%と小さなTMRしか示さない。本発表では、bcc-CoMn合金を中間層に用いたp-MTJとそのTMR特性を示すとともに、MnGa系p-MTJの最近の進展についても簡単に紹介する。

Perpendicular magnetic tunnel junctions (p-MTJs) are key devices for rich applications such as magneto-resistive random access memory, magnetic sensor, and high frequency devices. Not only do they be required to have proper magnetic properties for the applications, but they also need to have a high TMR ratio at operating temperatures. Tetragonal Mn-based alloys are one of distinctive and attractive perpendicular magnetic materials as the electrode materials for p-MTJs because of their small saturation magnetization, large coercivity, large perpendicular magnetic anisotropy, and small Gilbert damping factor. However, the p-MTJs utilizing Mn-based alloy as the ferromagnetic electrode have only exhibited small TMR at room temperature, still maximum of 60% even if FeCo interlayers were used. We have recently focused on bcc-Co based alloys as the interlayer material for MnGa-based MTJs in order to enhance further TMR. In this presentation, we demonstrate the p-MTJs utilizing bcc-CoMn interlayers and their TMR properties, and we briefly introduce recent progress for MnGa-based p-MTJs, as well.