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Tunnel Valve Flux Guide With Active Region AP Free Layer Structure and a Single Magnetic Layer Flux Guiding Element

IP.com Disclosure Number: IPCOM000016305D
Original Publication Date: 2003-Feb-02
Included in the Prior Art Database: 2003-Jun-21
Document File: 3 page(s) / 55K

Publishing Venue

IBM

Abstract

Disclosed is a tunnel-valve flux guide structure that has an anti-parallel (AP) free layer structure. During the fabrication process, one layer of the AP free layer structure is selectively oxidized to form the magnetic conducting flux guide which propagates flux from the air bearing surface to the sensing region. The fabrication sequence uses an insitu deposition of all the tunnel valve layers (pinned layer on the top structure), local ion milling to remove all layers of the tunnel valve down to the top layer of the ap free layer, and selective oxidation of the top layer of the ap free layer. The advantage of this design is two fold: 1) only the bottom free layer and the ap spacer layer and the bottom lead material are exposed at the abs or more specifically no gap barrier material is exposed at the abs 2) the net moment of the resulting flux guide layer is greater than the net moment of the ap layer free layer. These two points provide a more corrosion resistant sensor at the air-bearing surface (ABS) and a more efficient tunnel valve structure.

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  Tunnel Valve Flux Guide With Active Region AP Free Layer Structure and a Single Magnetic Layer Flux Guiding Element

A flux-guide structure in a magnetic sensor consists of an extended region of the sensing (free) magnetic layer which carries the sensed flux from the exposed area of the sensor (air-bearing surface (ABS) in a recording head sensor) into the active region of the sensor. This allows the active sensor to be fabricated away from the exposed area and therefore protected from possible degradation due to air exposure or other negative environments. Several methods can be employed to fabricate to flux-guide features of the sensor. A prior art flux guide structure formed by local oxidation of the pinned layer is shown in Figure 1.

bottom lead

top shield

top cap

top lead

bottom shield

afm layer

oxidized pinned layer

tunnel barrier

free layer

pinned layer 1

Figure 1. Prior Art Flux Guide

In this prior art, the flux guide is formed by ion milling through the cap layer and the afm layer of the tunnel valve sensor and endpointing into the pinned layer. This is followed by oxidation to render the remaining pinned layer non conducting and non permeable. This design exposes the tunnel barrier material and the free layer material to the abs and this design results in a flux guide element thickness that is equal the free layer thickness.

However, some tunnel barrier materials contain elements such as Mg, Ga, Zn, Sn, Hf, Mn which are oxidized to form the tunnelling layer. Consequently, these layers are more corrosive than standard Al oxide barriers, and as such the flux guide structure in

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the prior art would be prone to fabrication yield issues during the formation of the ABS. Also, because this prior art design has the flux guiding portion of the sensor and the free layer active region of the sensor with the same thickness, the efficiency of conducting flux into the active region of the sensor is marginal.

Here we disclose a flux guide structure invention that solves these problems is shown in Figure 2.

top shield

top cap

afm layer

pinned layer

tunnel barrier

oxidized free layer 1

Ru spacer

free layer 2 with thickness t2

bottom lead

top lead

bottom shield

free layer 1 with thickness t1

Fig.2: Disclosed flux-guide tunnel-valve structure

In this structure four elements are new. First, the free layer in the sensor active region is replaced by an AP free layer (layer 1 and layer 2 separated by Ru which causes antiparallel exchange coupling between layer 1 and layer 2). Second, the barrier layer does not extend to the ABS. Third, free layer 1 is oxidized locally above the flux guiding portions of free layer 2. Fourth, the flux guiding element of the sensor is composed of only magnetic free...