AVS 45th International Symposium
    Magnetic Interfaces and Nanostructures Technical Group Friday Sessions
       Session MI-FrM

Invited Paper MI-FrM3
Switching Field Measurements of Longitudinal Magnetic Recording Media

Friday, November 6, 1998, 9:00 am, Room 324/325

Session: Magnetization Dynamics and Magneto-Optics
Presenter: A. Moser, IBM Almaden Research Center
Authors: A. Moser, IBM Almaden Research Center
D. Weller, IBM Almaden Research Center
M.E. Best, IBM Almaden Research Center
Correspondent: Click to Email
Media stability is one of the key issues in the development of future high density magnetic recording media, as it determines the lifetime of a disk. At short time scales the coercivity strongly increases and recording information requires high write fields. Both, media stability and enhanced coercivity at short time scales can be examined using switching field measurements H@sub CR@ as a function of the magnetic field pulse width t. The data can be analyzed within the framework of the Arrhenius-Neel law using the equation H@sub CR@ = H@sub 0@ (1 - [C log(t f@sub 0@)]@super n@).@footnote 1@ Here, the constant C describes the stability of the media and is related to the viscosity parameter. H@sub 0@ is an intrinsic switching field related to the anisotropy field H@sub K@, f@sub 0@ is an attempt frequency (of the order of 10@super 9@ Hz) and n is an exponent which takes values between 1/2 and 1. By measuring H@sub CR@ over more than 9 decades in time using a novel experimental method, we can determine both the stability parameter C and the switching field H@sub 0@ for a series of CoPtCr media of different thicknesses.@footnote 2@ These samples have varying areal moment densities Mrt between 0.17 and 0.39 memu/cm@super 2@ and remanence coercivities H@sub CR@ between 500 and 2500 Oe at a pulse width of 1 s. It will be shown that H@sub CR@ can vary by more than a factor of 3 over the observed range of pulse widths. The results are compared to conventional signal decay measurements and to experimental and theoretical results found in literature.@footnote 3@ @FootnoteText@ @footnote 1@M.P. Sharrock, IEEE Trans. Magn. 26, (1990) 193. @footnote 2@Samples provided by M. Doerner, IBM Storage Systems Division, 5600 Cottle Rd., San Jose, CA 95193 @footnote 3@M.Yu, M.F. Doerner, D.J. Sellmyer, MMM-Intermag ?98, San Francisco, Jan. 6-8, 1998