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Magnetically Coupled Barberpole MR Head With Built In Longitudinal Bias Structure and Process

IP.com Disclosure Number: IPCOM000088741D
Original Publication Date: 1977-Jul-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 3 page(s) / 43K

Publishing Venue

IBM

Related People

Romankiw, LT: AUTHOR

Abstract

In a typical barberpole-biased head [*] shown in Fig. 1 with leads 9 and MR stripe 11, the biasing is accomplished by depositing a plurality of gold conductors 10 at a 45 degree angle to the width of stripe 11. Current I flows in stripe 11 from one conductor 10 to the conductors 10, taking the shortest path perpendicular to conductors 10. Upon entering a conductor 10, current I can be assumed to follow along its length. Since this type of bias still allows the magnetization to take one of two possible directions, the device may still be expected to exhibit Barkhausen noise. Here, use of a small external longitudinal bias eliminates the possibility of the two states and of Barkhausen noise.

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Magnetically Coupled Barberpole MR Head With Built In Longitudinal Bias Structure and Process

In a typical barberpole-biased head [*] shown in Fig. 1 with leads 9 and MR stripe 11, the biasing is accomplished by depositing a plurality of gold conductors 10 at a 45 degree angle to the width of stripe 11. Current I flows in stripe 11 from one conductor 10 to the conductors 10, taking the shortest path perpendicular to conductors 10. Upon entering a conductor 10, current I can be assumed to follow along its length. Since this type of bias still allows the magnetization to take one of two possible directions, the device may still be expected to exhibit Barkhausen noise. Here, use of a small external longitudinal bias eliminates the possibility of the two states and of Barkhausen noise.

A built-in magnetically hard film 21 or 44 (Figs. 2A-2C) provides a longitudinal bias, while conductors 10 provide the 45 degrees angle bias. Layer 22 is n magnetoresistive Ni-Fe layer, like stripe 11. In addition to built-in longitudinal bias, further improvement in the 45 degree angle bias is realized by making conductors 10 either entirely of electrically conducting magnetic material, such as a Ni-Fe alloy 24 (Fig. 2A), or of electrically conducting material 25 capped with a thin magnetic layer 34 or 44 (Figs. 2B and 2C). The magnetic layer comprising the conductor 10 can be made of either magnetically soft or hard material. The magnetic material should be deposited preferably in a magnetic field DF perpendicular to the length of conductors 10, as shown in Figs. 2A and 2B, although deposition can also be made in the absence of a field, particularly when the Fig. 2B version is used in connection with a soft magnetic film, such as Ni-Fe.

When the Fig. 2C version is used, particularly when layer 44 is of a hard magnetic material, such as CoPt or Fe(3)O(4), the layer 44 can be deposited in a longitudinal field along the easy axis (EA). In this case, when operated at low current through stripe 11, the longitudinal bias film 21 (Figs. 2A and 2B) is redundant and can be omitted.

The structure of Fig. 2B, when operated under constant relatively large current through stripe 11, has layer 34 on top of each conductor 10 oriented magnetically in direction DF perpendicular to the length of conductor 10 and thus, through magnetic coupling with film 22, greatly aids in orienting (biasing) film 22. In addition to improved magnetic operation of the device, the presence of cap layer 34 of magnetically soft Ni-Fe or hard Co-Pt or Fe(3)O(4) material on top of the Au, Cu, Al, Mo, Dr, etc., layer 25 results in an improved adhesion of SiO(2) or other dielectric gap material. (Adhesion of SiO(2) layer 23 to the Au or Cu stripes is not very good, yet adhesion of sputtered SiO(2) to Ni-Fe, Co-Pt, or Fe(3)O(4) is co...