Cu下地層上にスパッタしたCo-Pt合金膜の結晶構造と垂直磁気異方性

抄録

Cu underlayers were sputtered on mica and glass substrates at substrate temperatures T_s^Cu ranging from 20 to 300°C. Then, at a substrate temperature of 100°C, Co₇₅Pt₂₅ alloy layers were sputtered on them. The (111)-orientation of Cu underlayers on mica substrates was dramatically improved by elevating T_s^Cu above 200°C, while the Cu underlayers on glass substrates were hardly textured even at 300°C. Co-Pt alloy layers on highly (111)-oriented Cu underlayers were of (00.1)-oriented hcp structure, though a trace of (111)-oriented fcc phases was detected. In the Co-Pt/Cu/mica films, effective perpendicular anisotropy K_eff increased remarkably with rising T_s^Cu, in accordance with the development of (00.1)-oriented hcp phase. On the other hand, K_eff remained negative even at 300°C in the Co-Pt/Cu/glass films. No significant difference in K_eff was found between Co-Pt/Cu/mica and Co-Pt/Pt/mica films. The uniaxial anisotropy constants K₁ and K₂ were evaluated from torque curves. The enhancement of K_eff was due solely to the increase in K₁ and K₂ varied only a little with the development of texture.