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Theory of rotational processes in perpendicular media and application to anisotropy measurement

Zhou, H.J., Chantrell, R.W., Weller, D. and Ju, G.P. (2003) Theory of rotational processes in perpendicular media and application to anisotropy measurement. IEEE Transactions on Magnetics. pp. 1902-1907. ISSN 1941-0069

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Numerical and analytical calculations of rotational process in perpendicular recording media are presented. The work supports recent experimental studies that suggest that the measurement of rotational magnetization processes can be used to determine the value of the anisotropy constant. An expression for the rotational magnetization for a noninteracting system is derived taking into account the dispersion of K and the easy-axis orientation. The calculations show that the experiments determine the mean value of H-K, essentially independent of the angular dispersion. A numerical (Monte-Carlo based) micromagnetic model is used to study the effects of magnetostatic and exchange interactions at nonzero temperatures. It is shown that for small values of KV/kT, irreversible magnetization processes take place, which precludes the use of the rotational magnetization method to determine K values. This effect is enhanced by the presence of the magnetostatic interaction. However, the presence of exchange interactions is found to enforce coherent rotation in small fields, reducing the irreversible processes and allowing the determination of H-K. Under these circumstances, it is shown that the exchange does not significantly affect the value of HK, and that a well-defined demagnetization correction of 4piM is appropriate. Finally, a comparison with experimental data gives good agreement for multilayer and granular media and shows the role of domain formation on the rotational magnetization process.

Item Type: Article
Copyright, Publisher and Additional Information: © 2003 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.
Keywords: anisotropy,micromagnetics,perpendicular media,rotational magnetization
Institution: The University of York
Academic Units: The University of York > Physics (York)
Depositing User: Repository Officer
Date Deposited: 18 Dec 2006
Last Modified: 19 Apr 2016 21:03
Published Version: http://dx.doi.org/10.1109/TMAG.2003.813780
Status: Published
Refereed: Yes
URI: http://eprints.whiterose.ac.uk/id/eprint/1835

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