Study of microstructures and magnetic properties of FePt/Os multilayer films

• Main Authors: Chen, Shih-Yuan, 陳士元
• Other Authors: Wu, Jenn-Ming
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/88538950780326730020

博士 === 國立清華大學 === 材料科學工程學系 === 98 === The FePt/Os multilayer flims were deposited on Si(100) and glass substrates with/without a Os spacer layer at room temperature by dc-magnetron sputtering. The oscillation of the interlayer exchange coupling as a function of the Os spacer thickness and the GMR (giant magnetoresistance) effect has been widely studies in recent years. For example, Fe/Cr, Co/Ru, Co/Cr systems have been extensively discussed by different authors. The study of magnetoresistance and interlayer coupling of FM/Os/FM trilayer films (FM = FePt, CoFe, Co, Fe, CoFeB, CoFeC), the FM/Os trilayers films with suitable spacing layer (Os) thickness have been prepared on Si(100) substrates. We report the oscillation behavior of antiferromagnetic coupling as a function of the Os thickness and the magnetoresistance effect. The mechanism and growth process of FePt film on a membrane of anodized aluminum oxide have been studied by SEM observation. The additional Au buffer layer will promote the ordering process of FePt films, reduce ordering temperature and enhance the coercivity. For effects of Os inserted layers on the microstructure and magnetic properties of the FePt films, The thermal stability, interlayer diffusion, microstructures and magnetic properties of FePt(100nm) single-layer and multilayer FePt/Os films on Si(100) and glass substrates with/without a 10-nm-thick Os underlayer have been studied as functions of the annealing temperatures between 400 and 800°C. The insertion of a thin Os layer into the FePt and Si(100) interface results in better thermal stability. No diffusion evidence was found in samples with a thin Os layer and t ≧ 1 nm after a post-annealing procedure, as seen from X-ray, transmission electron microscopy, and magnetic studies. The Os underlayer can effectively prevent the diffusion of the intermixing between the FePt layer and the Si(100) substrate for temperatures up to 700°C. The FePt/Os multilayer films showed enhanced coercivity significantly due to the reduced grain size. The texture of hard magnetic layers and the grain size of the multilayer films can be well controlled by both annealing temperature and thickness of the FePt layer by an Os space layer. The enhancement of Hc can be understood from the fact that for a FePt film with an Os spacer layers, the increasing number of Os layer will inhibit the two-dimensional grain growth at the thickness direction of FePt films and enriches the grain boundary. We have experimentally demonstrated that even with a very thin 1 nm Os spacer layers, the [FePt(x)/Os(t)]n multilayer films can exhibit good hard magnetic properties and are attractive candidates for ultrahigh density magnetic recording media.