Ni_<80>Fe_<20>/Al-Oxide/Co接合における磁気抵抗効果のAl-Oxide厚依存性  [in Japanese] Al-Oxide Thickness Dependence of the Magnetoresistance Effect in Ni_<80>Fe_<20>/Al-Oxide/Co Junctions  [in Japanese]

Ferromagnetic tunneling junctions of Ni_<80>Fe_<20>/Al-Oxide/Co with various Ni_<80>Fe_<20> and Al-oxide thicknesses were fabricated by magnetron sputtering using metal masks. The thicknesses of Ni_<80>Fe_<20> were 70, 100, 200, 500, and 1000 Å. The thicknessed of the Al layer ranged from 7 to 80Å, and the Al oxide films were formed by natural oxidization. The thicker the Ni_<80>Fe_<20> lyaer, the larger the optimum Al thickness for the TMR ratio. On the other hand, when the thickness of Ni_<80>Fe_<20> was constant, the TMR ratio decreased with increasing Al thickness. To clarify the reason for this, AFM images of the Ni_<80>Fe_<20> surface were measured. The surface roughness of Ni_<80>Fe_<20> increased with increasing Ni_<80>Fe_<20> thickness.