Time dependence in perpendicular media with a soft underlayer

In this paper we describe measurements of magnetic viscosity or time dependence in magnetic thin films suitable for use as perpendicular recording media. Generally, such effects cannot be measured using conventional magnetometry techniques due to the presence of a thin (0.1 /spl mu/m) soft underlaye...

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Bibliographic Details
Published in:IEEE transactions on magnetics 2004-07, Vol.40 (4), p.2504-2506
Main Authors: Dutson, J.D., Jing Wu, O'Grady, K., Woolsey, N.C., Kubota, Y., Platt, C.L.
Format: Article
Language:English
Subjects:
Anisotropic magnetoresistance
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Energy barrier
Exact sciences and technology
Magnetic field measurement
Magnetic films
Magnetic properties and materials
Magnetic thin films
Magnetism
Magnetization
Perpendicular magnetic recording
Physics
Thermal resistance
Time measurement
Viscosity
Volume measurement
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Summary:In this paper we describe measurements of magnetic viscosity or time dependence in magnetic thin films suitable for use as perpendicular recording media. Generally, such effects cannot be measured using conventional magnetometry techniques due to the presence of a thin (0.1 /spl mu/m) soft underlayer (SUL) in the media necessary to focus the head field. To achieve our results we have developed an ultrastable MOKE magnetometer, the construction of which is described. This has enabled us to measure nominally identical films with and without the presence of the SUL. We find that the presence of the SUL narrows the energy barrier distribution in the perpendicular film increasing the nucleation field (H/sub n/), reducing the coercivity (H/sub c/) and results in an increase in the squareness of the loop. This in turn results in an increase in the magnitude of the viscosity in the region of the H/sub c/ but that the range of fields over which the viscosity occurs is reduced.
ISSN:0018-9464
1941-0069
DOI:10.1109/TMAG.2004.832259