Microstructure and orientation of iron crystals by thermal chemical vapor deposition with imposition of magnetic field
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Satoshi Awaji, Kazuo Watanabe, and Eiji Aoyagi Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Japan, 980-8577 (Received 14 May 2002; accepted 13 August 2002)
Iron crystals were deposited by thermally activated chemical vapor deposition with imposition of magnetic field. In this study, the deposition was conducted by imposing a magnetic field up to 3.5 T in a temperature range between 0.48 and 0.51 of TmFe (melting point of iron), which is below the Curie point of iron (0.58 TmFe). The microstructures and crystal orientations of the deposits were investigated. In the deposition process, island-shaped crystals were formed on a scale of several microns; then a film was grown by their coalescence. As the magnetic field magnitude increased, population of the island-shaped crystals having a cubic shape increased. Simultaneously, their -scanned (200) profile became sharper. Their degree of (100) preferred orientation was dependent on the magnetic field up to 3.5 T, which is usually high enough for the saturated magnetization of iron crystals. However, when the substrate was placed parallel to the magnetic field, (100) preferred orientation was not observed for the island-shaped crystals. A large and bimodal -scanned (110) profile having sharp peaks was obtained when the substrate was inclined 45° to the field. Preferred (100) orientation was not obtained from the iron films, for which two reasons were pointed out. The first is the secondary grown crystals on the island-shaped crystals having different orientations, and the second is the observed zone III grain structure of the films, where grain boundary migration occurred.
I. INTRODUCTION
Recent progress in cyrogen-free superconducting magnet technologies has enabled extensive use of high magnetic field,1 which had been utilized mainly for investigation of magnetic properties of matters.2 On behalf of these magnets, various attempts are now performed for fabrication of materials for applications of high magnetic field. In the area of functional polycrystalline thin films, their crystal orientations are closely related to their properties. For example, in an area of magnetic recording materials, excellent squareness factors in B–H curves are obtained from the films with well-oriented crystals.3 It is expected that imposition of magnetic field during the fabrication process can become one of the effective methods for obtaining the specific crystal orientations. Among the various film fabrication processes, electrolytic deposition from an aqueous solution and vapor deposition are the major methods. Metallic films of Ni4 and Zn5 were fabricated by electrolysis with imposition of a)
Present address: Sumitomo Metal Inc., Kashima, Ibaraki, Japan. Graduate student at Tohoku University. J. Mater. Res., Vol. 17, No. 11, Nov 2002
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magnetic field. An increased degree of c-axis crystal orientation in the Zn film was reported. There were a number of attempts at the vapor deposition pro
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