Browse Prior Art Database

Biased Magnetic Read Head

IP.com Disclosure Number: IPCOM000051851D
Original Publication Date: 1981-Mar-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Klaassen, KB: AUTHOR

Abstract

To increase the efficiency of a readback magnetic head, the head is magnetically biased to a level sufficiently high to attain an increased effective permeability of the head magnetic circuit. The magnetic bias is also sufficiently low so as not to erase the recorded data.

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 86% of the total text.

Page 1 of 2

Biased Magnetic Read Head

To increase the efficiency of a readback magnetic head, the head is magnetically biased to a level sufficiently high to attain an increased effective permeability of the head magnetic circuit. The magnetic bias is also sufficiently low so as not to erase the recorded data.

The magnetic bias is applied to the head in the form of a permanent magnetic field (DC bias); or an alternating magnetic field (AC bias) having a repetition frequency greater than the useful frequency band containing the readback data. A DC bias can be generated by the remanent magnetization of the head after a write operation, and the magnitude of this DC bias may be increased by the application of DC current through the head coil.

The effect of magnetic bias on the effective permeability Mu of the magnetic circuit of a recording head, used for readout of data, is illustrated in Figs. 1A-1C. Fig. 1A depicts the curve for a demagnetized read head having an effective permeability Mu.(1) Fig. 1B illustrates the application of a DC bias to a thin film read head, with an effective permeability Mu(2) resulting from irreversible domain wall changes. Fig. 1C shows the application of an AC bias applied to a read head resulting in an effective permeability of Mu(2).

The effects of increasing efficiency and increasing erasure are illustrated respectively in Figs. 2A and 2B. Assuming the application of a 70 MHz AC bias current through a thin film head, Fig. 2A indicates increasin...