Time dependence in perpendicular media with a soft underlayer

• Published in: IEEE transactions on magnetics Vol. 40; no. 4; pp. 2504 - 2506
• Main Authors: Dutson, J.D., Jing Wu, O'Grady, K., Woolsey, N.C., Kubota, Y., Platt, C.L.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY IEEE 01.07.2004; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• 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; Magnetic materials; perpendicular media; Magnetic viscosity; MOKE magnetometer
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2004.832259

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.