Magnetic properties of CoPt thin film sputtered at room temperature

• Main Authors: Po-Yi Li, 李柏毅
• Other Authors: Huang-Wei Chang
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/29342606802856435718

碩士 === 東海大學 === 物理學系 === 102 === To attain a single-layer alloy film showing high perpendicular magnetic anisotropy (PMA) and very flat surface obtained from room-temperature (RT) deposition is of importance for perpendicular spintronic applications (PSA). In order to achieve smooth surface and high PMA in single-layered alloy film, in our present work, CoPt thin films are sputtered onto Pt/Ta-buffered glass or SiO2/Si(100) substrates at RT. First, effect of growth temperature (Tg=RT-600 oC), post-annealing temperature (Tp =RT-450 oC), and thickness of underlayers on the magnetic properties of Co80Pt20 thin films are investigated. Co80Pt20 films with high PMA sputtered at RT are successfully obtained by introducing both Pt(20 nm) and Ta(20 nm) underlayers on either the glass or SiO2/Si(100) substrate. Co80Pt20 films deposited at RT-600oC or post-annealing at 100-450oC also exhibit good PMA. Co80Pt20 film on Pt(10 nm) and Ta(5 nm) shows comparable PMA to that on Pt(20 nm) and Ta(20 nm). On the other hand, effect of underlying, Co50Pt50 thickness, Co100-xPtx (x=40-60) composition, post-annealing temperature (Tp =RT - 450 oC) on the magnetic properties for Co50Pt50 thin films are also studied. The experimental results that a tetragonal Ta layer play a crucial role in enhancing the face-center-cubic Pt(111) texture, then enhancing hexangonal CoPt(0002) texture, and besides, in reducing the surface roughness of CoPt film. As a result, 10-nm-thick Co50Pt50 films sputtered onto Pt(10 nm)/Ta(5 nm) buffered on SiO2/Si(100) substrate at RT display very flat surface with roughness below 0.35 nm and high PMA with low coercivity (Hc⊥= 433 Oe) and high squarness ratio (S=0.96). Co50Pt50 films with 2-20 nm in thickness also exhibit good PMA and smooth surface morphology. Besides, RT-deposited Co50Pt50 films post-annealed at 100-450 oC remains good PMA, revealing a good thermal stability of PMA for this studied Co50Pt50 films. Besides, good PMA and smooth surface morphology also achieved for 5-nm-thick Co100-xPtx films with x = 40-60 indicates a wide composition range for PSA. Finally, Co50Pt50 (3 nm)/Ru(1.2 nm)/Co50Pt50(3 nm)/Pt(10 nm)/Ta(3 nm)/SiO2/Si(100) show a typical antiferromagnetic coupling of RKKY. The results of present study suggest that studied CoPt films have great potential for perpendicular spintronic devices applications.