The effect of Sm or Dy doping on the magnetic properties of CoTb thin films and their possibility for application to the thermo-magnetic recording media

• Main Authors: Chen, Yean-zhaw, 陳彥兆
• Other Authors: Kuo, Po-cheng
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/60102099514542218740

碩士 === 國立臺灣大學 === 材料科學與工程學研究所 === 89 === With new recording media for “near-field optical writing and magnetic flux reading” , it is practicable to overcome the threshold of optical diffraction limit and increase the recording density. In this study, a single layer of 1000 Å amorphous thin-film of CoTbDy and CoTbSm alloys were prepared by DC magnetron sputtering. The alloy film is sand- wiched between two 150 Å SiNx protective layers which are prepared by RF magnetron sputtering so as to prevent the alloy film from oxidation. The substrate is glass. Sputtering condition would affect the alloy composition and the film magnetic properties. From the XRD and TEM analysis, the structure of the as-deposited-films were all amorphous. The addition of light rare-earth element, Sm, would rise the saturation magne- tization of CoTb alloy film, but the magnetic anisotropy of CoTbSm film is parallel to the film plane and the out-plane coercivity is lower than 1 kOe. On the other hand, the addition of heavy rare-earth element Dy would increase the out-plane remanent magnetization and the out-plane squareness of the film. From this study, the magnetic properties of Dy dopped CoTb film are better than those of CoTb or CoTbSm films. The thermomagnetic analysis shows that the Curie temperature of the CoTbDy film is higher than 460 oC, this is also higher than the recrystallization temperature of the film. The out-plane coercivity of Co71Tb14Dy15 film is about 1.8 kOe , out-plane remanent magnetization is about 145 emu/cm3 and out-plane squareness equals to 0.85. At 200 oC, the out-plane coercivity of the film is lower than 50 Oe. This film is suitable for GMR head sensing and SIL thermomagnetic writing.