Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/17664
Title: Preparation and Characterization of Sputtered SmCo5 Thin Films for Magnetic Recording Media
Authors: ZHANG LINA
Keywords: Thin films, SmCo5, magnetism, recording media
Issue Date: 4-Jan-2010
Source: ZHANG LINA (2010-01-04). Preparation and Characterization of Sputtered SmCo5 Thin Films for Magnetic Recording Media. ScholarBank@NUS Repository.
Abstract: The progress in the magnetic storage technology largely depends on the development of magnetic storage media (magnetic films that store information). For ultra-high density recording media, a large anisotropy is necessary in order to scale down the grain size because of the required thermal stability. SmCo5 is the ultimate candidate because of its uniaxial magnetocrystalline anisotropy (Ku=1.1~2.0×108 erg/cm3) which is the highest among all the hard magnetic materials. SmCo5 based thin films allow significant reduction in the grain size from currently about 7-9 nm in Co-alloys to about 2-3 nm based on the superparamagnetic limitation. Therefore, SmCo5 thin films with fine grains, specific texture and high coercivity are of a high interest for achieving an ultra-high areal density and good recording performances. This thesis focused on the fabrication of magnetron-sputtering derived SmCo5 thin films for magnetic recording using a layer engineering approach. The study has shown that the structure and the magnetic properties of SmCo5 thin films can be greatly influenced by the texture and the surface morphology of the underlayer and deposition condition. The study has resulted in suitable multilayer designs and deposition control methods in order to obtain SmCo5 films with the desired structure and magnetic properties. Three layer configurations were studied: (11 - 2 0) textured SmCo5 / (002) textured Cr / glass; (0001) textured SmCo5 / (111) textured Cu / amorphous-like Ta / glass; (0001) textured SmCo5 / (211) textured Ni4W / amorphous-like W / glass. With the first configuration, a nanocrystalline SmCo5 film was obtained with a high in-plane intrinsic coercivity up to 26.5 kOe and a large in-plane magnetic III anisotropy. The film was deposited on an economical glass substrate at a relatively low temperature of 400 oC. With the second configuration, a Ta seed layer was found effective in improving the crystallinity, texture and surface morphology of the Cu underlayer. The optimal Ta seed layer was a thin, continuous and amorphous-like layer with a thickness of 4 nm. A highly (000l) textured SmCo5 thin film (with a small Dq50 value of 3.2 o) exhibiting large perpendicular anisotropy and high out-ofplane intrinsic coercivity around 20 kOe was obtained on the Cu / Ta dual underlayer. The deposition temperature for SmCo5 to having the (0001) texture was as low as 325 oC. In the last configuration, a nanocrystallined and (211)-textured Ni4W / W dual underlayer was found to be able to induce SmCo5 thin films with perpendicular anisotropy. This is due to the Ni4W-(211) plane having a hexagonal structure which is similar to that of the SmCo5-(0001) plane. The Ni4W underlayer can be as thin as 13 nm. A maximum out-of-plane intrinsic coercivity of 15.5 kOe was achieved in SmCo5 thin films grown on Ni68W32 underlayer with Ni4W clusters. The use of the Ni4W underlayer has not been reported by other research groups so far. Based on the obtained magnetic properties, SmCo5 / Ni / Ni4W / W film was found to be a promising hard/soft double-layered design for perpendicular recording applications.
URI: http://scholarbank.nus.edu.sg/handle/10635/17664
Appears in Collections:Ph.D Theses (Open)

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