Property study of ferromagnetic materials for optical media
Lim, Cheng Huat.
Date of Issue2009
School of Materials Science and Engineering
In this work, the properties of ferromagnetic material, TbFeCo was studied. Among all the rare earth transition metals available, TbFeCo is the most popular and widely used in magneto-optical recording. At the beginning of the project, the transition phase of TbFeCo was investigated. TbFeCo was studied using Differential Scanning Calorimetry and the material was found to have a metastable state with activation energy of 1.12eV. X-ray Diffraction analysis was next conducted and from the results, the material remained in its amorphous state when heated to a temperature as high as 450oC. Subsequently, the influence of the thickness of TbFeCo on its magnetic properties and optical constant was investigated. Thicknesses in the range of 5 nm~50 nm were used as these correspond to the thicknesses used in the magneto-optical recording. The refractive index, measured by ellipsometer at the wavelength of 650 nm (red light), was instable when the thickness of TbFeCo was less than 10nm. It was advisable to deposit at least 10 nm of TbFeCo for magneto-optical application. With the help of spectrophotometer, it was found that to obtain a high reflectance value in the wavelength of 650 nm, thickness of TbFeCo must be in the range of 30 nm~40 nm. In addition, to achieve remanence and coercivity, a thickness of TbFeCo of 25 nm is required. Finally, thermal stability of the material was studied. The Curie temperature of the material was found to be at 141oC. Upon that temperature, the material became unstable and was unable to be used for magneto-optical recording purposes.
Final Year Project (FYP)