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Edge Bias of Magnetoresistive Films

IP.com Disclosure Number: IPCOM000084171D
Original Publication Date: 1975-Sep-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Mazzeo, NJ: AUTHOR [+2]

Abstract

In magnetoresistive read heads which consist of a film sensor and bias film, there is a problem which causes signal level changes as a function of time. These changes are due to reversal domains (magnetic) which grow and change due to varying applied fields. These are known as Barkhausen noise, creeping domain walls, etc.

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Edge Bias of Magnetoresistive Films

In magnetoresistive read heads which consist of a film sensor and bias film, there is a problem which causes signal level changes as a function of time. These changes are due to reversal domains (magnetic) which grow and change due to varying applied fields. These are known as Barkhausen noise, creeping domain walls, etc.

Fig. 1 shows a top view of a magnetoresistive unit. Fig. 2 is an end view of Fig. 1. The magnetoresistive unit includes a magnetoresistive sensor 11 composed of NiFe, a bias stripe 12 composed of a magnetically hard material, such as NiFeCr, separated by an insulating layer 13 of SiO or equivalent.

One apparent cause of the domain walls which cause Barkhausen noise, is the higher coercive force (Hc) of the films directly under the gold or copper conductor leads 10. These walls once present are easily moved by applied external fields. In Figs. 1 and 2, walls 14, which separate reversed magnetized domains cause signal variation in active sensor 11.

In Fig. 3, the device of Figs. 1 and 2 is modified by thickening layer 12 in small regions 20 beneath each lead 10.

To prevent walls 14 from propagating into the active sensor region in Fig. 3, regions 20 adjacent to each lead 10 but part of sensor 11 are saturated by the thickening there of layer 12. This reduces the active length of sensor 11 about 10% or less, but provides a barrier region to inhibit the Barkhausen effect.

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