Herbert Schewe

Observation of particle trajectories in an HGMS single-wire system

Trajectories of paramagnetic particles were observed experimentally in single-wire HGMS by means of a television system. The observed trajectories were used as a test for the two models of fluid flow, namely potential (inviscid) flow and laminar (viscous) flow. Results of these measurements which were carried out for small Reynolds numbers (0.1 < Re < 0.5) show that the trajectories near a clean collecting wire are described correctly quantitatively by means of the laminar flow model.

Industrial applications of magnetoresistive sensors

Abstract Magnetoresistive sensors are commonly used for determining data in rigid disk drives, angular or linear positions, currents and magnetic fields. The magnetic field itself is the quantity which will be measured and the desired information about position, angle, distance, number of turns, rotational speed, defect detection, pressure, moment of force and tactile strength can be evaluated from the strength or direction of the field.

A new read/write concept for vertical recording

A novel read/write concept for vertical recording in rigid disk drives is described that makes it possible to write very short magnetic transitions in double-layer media. The occurrence of magnetic saturation zones inside the poles of the thin-film head are chosen so that the head writes an asymmetrical magnetic transition with a very steep field edge. The readback signal reproduced by the combination of an asymmetrical head and an asymmetrical transition is defined by the reciprocity theorem. The asymmetry of the reading characteristics of the head is determined by the design. If the poles and the gap are suitably dimensioned, the asymmetrical effects can be made to compensate each other, and nearly antisymmetrical readback pulses are produced. Hence this head/disk combination makes possible recording densities of more than 100 Mb/in/sup 2/. >

Thin-film inductive heads for perpendicular recording

A modified thin-film magnetic head for perpendicular recording in rigid disk drives with improved read/write characteristics, especially at high areal bit densities, is presented. The head on which the modified design is based is described. It combines the advantages of single-pole heads and thin-film heads, writing with the sharp field edge of the leading pole and reading like a thin-film head. To increase the writing efficiency and improve the yield, the sequence of magnetic layers in the head is changed; the second layer of the four-layer head is embedded in the substrate, where it can be placed much closer to the pole tip of the first layer. The improved write capability depends mainly on the position of the embedded layer. In addition, there results an improved magnetic flux guidance from the embedded layer into the pole tip layer, providing the potential for a significant improvement in fabrication yield. The embedded-layer approach also allows a further increase in areal density. The results of read/write tests and the write-wide and read-narrow characteristics are presented. >

Three-dimensional magnetic field measurement of a modified thin-film magnetic head for vertical recording by means of Lorentz-tomography

The method of Lorentz tomography with an electron beam as a microprobe, combined with an analytical reconstruction procedure, has been successfully adapted to thin-film heads for vertical recording. It is noted that the measured results can be used as a basis for adjusting the magnetic parameters of the thin-film head to achieve good agreement with corresponding FEM or BEM (finite element or boundary element method) calculations. It is concluded that Lorentz tomography can be used as an important tool in the design of thin-film magnetic heads. >