Bill R. Baker

Nonlinear transition shift and overwrite frequency dependence

A simple analysis is used to relate nonlinear transition shift to the large range of overwrite values observed for different densities of the background and overwriting data. Fields from old transitions in front of the head shift the new data locations giving the measured variations.

Electrostatic popping in AMR and GMR heads

Dielectric breakdown of insulating layers between the MRE (magneto resistive element) and the conducting shields generates another type of base line shift or popping noise in MR heads. Pulse shapes are similar to those of thermal asperities, but they can be bipolar and can occur without a disk. Measurements illustrate the difficulties of characterizing these pulses. A physical model is proposed to explain the behavior, and a simple SPICE simulation shows similar pulse behavior.

Servotrackwriter with improved positioning system

An optical noncontact method eliminates the resonances generated by mechanical interaction of the HDA arm with a conventional pushpin. Errors due to air turbulence in a laser interferometer are avoided by using an encoder with one nanometer resolution.

Long wavelength response of elliptical reproduce heads

Long wavelength response characteristics for the class of elliptical reproduce heads are calculated. Simple series solutions are obtained for a flat recorded medium, and numerical methods are used for a tape wrapped over the head at arbitrary contact angles. Special eccentricities of the ellipse yield classical results. Many geometries lead to low frequency bumps on the response curve.

Green's function for magnetic shielding by a permeable layer

The flux distribution excited in a permeable slab by a current filament is found by means of generalized Fourier transforms. Induction components are expressed in terms of an incomplete beta function, and practical computation methods are described. Design results including maximum values of flux in the slab and the attenuated field behind the slab are given graphically for a range of permeability and geometric parameters. >

Thermal transfer in magnetooptic printing of servo patterns

A new magnetooptic method for rapid printing of servo patterns on magnetic disks is studied with respect to heat transfer. Because large areas are printed with one laser pulse and patterns resemble gratings more than spots, the requirements differ from conventional magnetooptic recording. Dependence on several system parameters is examined. Measurements are shown from a pattern printed by a media vendor.

Geometry of printed servo on perpendicular disks

Either perpendicular or longitudinal media can be magnetically printed with the final servo pattern of a disk drive. A simple analytical model provides an overview of the roles of geometry and magnetic properties in successful transfer. The more uniform geometry of compound phase patterns avoids the large line and space variations of conventional Gray codes.