Browse Prior Art Database

Thin Film and Thin Film Ferrite Hybrid Magnetic Heads

IP.com Disclosure Number: IPCOM000083487D
Original Publication Date: 1975-Jun-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 4 page(s) / 75K

Publishing Venue

IBM

Related People

Romankiw, LT: AUTHOR [+3]

Abstract

Vertical thin film and thin-film/ferrite hybrid magnetic read/write heads are batch fabricated by sandwiching a conductive spiral winding between magnetic pole pieces.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 45% of the total text.

Page 1 of 4

Thin Film and Thin Film Ferrite Hybrid Magnetic Heads

Vertical thin film and thin-film/ferrite hybrid magnetic read/write heads are batch fabricated by sandwiching a conductive spiral winding between magnetic pole pieces.

Each head basically includes two layers of high-permeability material between which is a layer of highly conductive metal, which is either chemically etched or electroformed in the form of a spiral. The high-permeability material may be either a deposited alloy such as permalloy, sheets of an alloy such as permalloy, or ferrite. The spiral conductor forms a multiturn winding for the purpose of sensing changes of magnetization in the horseshoe magnet formed by the pole pieces, or for inducing a magnetization in the pole pieces. A conductive jumper is applied to connect the inside of the spiral winding to a point outside the spiral to complete the circuit. The jumper may be a wire which is attached to the film or may be an additional deposited layer. If fewer turns are required than are provided by the complete spiral pattern, the jumper may be attached to a point other than the inside end of the spiral.

The principle of operation of the head is the same as that of a conventional ring head with a wound coil. In the reading mode, a difference in magnetic potential from the recorded media across the gap (formed by the uppermost leg of the spiral film winding) causes magnetic flux to pass down through one of the magnetic layers, through the center of the spiral winding, and up through the second magnetic layer. A voltage is induced in the winding which is proportional to the number of turns and the time rate of change of magnetic flux. Some of the flux will cross the gap before reaching the center of the winding so that the voltage induced in the interior turns will be somewhat less than that in the outside turns. The efficiency of the head is therefore improved by a) keeping the turns spacing of the spiral as narrow as possible, b) separating the two magnetic layers as far as possible, and c) keeping the thickness and permeability of the magnetic layers high.

In the writing mode, current is passed through the spiral winding, causing a magnetic potential in the magnetic layers, and a resulting magnetic flux which passes over the gap and magnetizes the tape. The same design considerations which affect the efficiency of the reading mode are important also in writing.

Figures A and B show a version of the head which is fabricated by electroplating both the magnetic layers and the conductive winding. (The layers could also be vacuum deposited proportional to). The fabrication process is as follows:

1) Metallizing an oxidized Si wafer or other suitable dielectric substrate (with relatively high thermal expansion coefficient and high thermal conductivity) with 100 to 300 angstroms of Ti or Cr and approx. 300 angstroms of Cu or permalloy at 150 to 200 degrees C by evaporation. Alternatively, the dielectric can be metallized...