スピンバルブ膜の構造と磁気特性に影響を及ぼすTa/Ni-Fe下地層の成長過程

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The structure and magnetic properties of Mn-Ir/Co-Fe based bottom-type spin valves (SVs) were investigated as a function of the under-layer thickness. Surface morphology of Ta/Ni-Fe under layers was also investigated with in-situ STM. The SV characteristics, such as magnetoresistance (MR) ratio and interlayer ferromagnetic coupling field (H_<in>), strongly depend on the underlaid Ni-Fe thickness (d_<Ni-Fe>). The MR ratio gradually increases with decreasing d_<Ni-Fe> above 20 Å because of the reduction of shunting current in the Ni-Fe layer. On the contrary, the MR ratio decreases with decreasing d_<Ni-Fe> below 20 Å. The H_<in> drops below 20 Å of d_<Ni-Fe> and shows relatively small values (10 to 20 Oe). These changes of SV characteristics correspond closely to change in film structure: a strong fcc (111) texture of the SV is observed when d_<Ni-Fe>=20 Å, but it vanishes when d_<Ni-Fe> < 20 Å, meaning the grain size is reduced. The surface morphology of a Ta/Ni-Fe under layer also changes drastically at d_<Ni-Fe>=20 Å. Distinct grains are observed on the surface of the Ni-Fe under layer on Ta only when d_<Ni-Fe> = 20 Å. This indicates that inter-diffusion of the Ni-Fe layer is less than 20 Å thick with a Ta layer. We conclude that the drastic change of film structure resulting in the change of SV characteristics is due to the inter-diffused Ni-Fe-Ta layer, which promotes the grain growth of the remaining Ni-Fe layer and the SV grown on it.
社団法人日本磁気学会の論文
2001-04-15

スピンバルブ膜の構造と磁気特性に影響を及ぼすTa/Ni-Fe下地層の成長過程

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