Browse Prior Art Database

Low Noise Thin Film Sensors for Magnetic Recording

IP.com Disclosure Number: IPCOM000088742D
Original Publication Date: 1977-Jul-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Di Stefano, TH: AUTHOR

Abstract

In magnetic recording, a problem which limits speed and resolution results from Barkhausen noise generated in thin-film read heads when a domain wall 13 in the figures jumps from one pinned position to another, generating an output voltage pulse.

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Low Noise Thin Film Sensors for Magnetic Recording

In magnetic recording, a problem which limits speed and resolution results from Barkhausen noise generated in thin-film read heads when a domain wall 13 in the figures jumps from one pinned position to another, generating an output voltage pulse.

Such Barkhausen noise is reduced by the use of a thin film of conductive material to damp the motion of the domain walls 13. Fig. 1 shows a cross- section through a thin-film head incorporating a conductive film 10. Film 10, typically about 1000 angstroms thick and composed of a metal such as copper, is separated from a ferromagnetic film 11 (about 0.7 - 1 mu thick) by a thin insulating layer 12. Film 11 may comprise a magnetoresistive material such as permalloy (nickel:iron, 80:20), and layer 12 is typically about 500 angstroms thick and composed of silicon-nitride. Layer 12 is used to separate the area of film 11 used for sensing from layer 10. Layer 12 should be thick enough so that the active area of film 11 is not significantly disturbed by the copper conductive layer.

Operation of layer 10 in damping domain wall motion is illustrated in Fig. 2, showing the fringing fields 14 from a moving domain wall 13. Eddy currents in film 10 retard the motion of fields 14, which in turn act to retard the domain wall motion. Layer 10 should not be so thick as to slow the overall response time of sensor film 11. A reasonable compromise is one in which the thickness of the conduct...