The continuous and rapid increase of areal density in magnetic data storage systems required a continuous increase of the coercivity of the storage media. In order to be able to record on these everhigher-coercivity media, new soft magnetic materials for pole tips with increased magnetic moment had to be developed. Significant progress has been made during the last few years in electroplating alloys with high saturation magnetic flux density for use in writing heads. We review recent progress made in this area, with particular emphasis on the work done at IBM since the review paper on the subject was published in this journal in 1998 by Andricacos and Robertson. Reviewed here are the high-moment alloys of NiFe, particularly in the very high iron range [an extension of permalloy (Ni 80 Fe 20) and Ni 45 Fe 55 ]; very-high-cobalt CoFeCu alloys; ternary CoNiFe; and binary iron-rich CoFe alloys. With the latter binary alloy films, we have demonstrated that it is possible to reach by electroplating the saturation flux density limit of 2.4-2.5 T reported for cast alloys. Since the electroplating of good-magneticquality iron-rich CoFe alloys posed a considerable challenge, the behavior of the CoFe plating system was studied in detail, using in situ surface pH measurements and a rotating-cylinder Hull cell.

Strong in-plane magnetic field pulses of 2 -4.4 ps duration are used to study magnetization reversal in perpendicularly magnetized Co͞Pt films. Ring domains, reminiscent of the field contour during exposure, are observed later with Kerr microscopy. Their radii represent switching fields which are in quantitative agreement with the coherent rotation model. The observation of intrinsic transition broadening is attributed to the existence of static and dynamic fluctuations of the magnetic anisotropy. [S0031-9007(98)07344-X]

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As we move to higher data rates and higher areal densities, nonlinear effects start to determine the data patterns written on a hard disk. In this context it is necessary to develop methods that can help to determine the origin of nonlinear effects, e.g., that can help to distinguish between nonlinear effects caused by areal density from transient effects caused by high data rates. In this article we concentrate on the latter and show data for nonlinear timing shift measured directly on the air bearing surface of recording heads by means of time resolved magneto-optical Kerr microscopy. We compare the data to a simple t/(t+τ) model for the head field rise time.

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