Browse Prior Art Database

AP spin valve with improved signal using Si in one pinned layer for improved DR/R and Sheet Resistance

IP.com Disclosure Number: IPCOM000014602D
Original Publication Date: 2002-Jan-27
Included in the Prior Art Database: 2003-Jun-19
Document File: 6 page(s) / 158K

Publishing Venue

IBM

Abstract

The pinned 1 layer of an AP spin valve adds stability to the structure, but at the cost of lower DR/R. This is partly due to simple shunting--the extra layer pulls electrons away from the active layers. A secondary effect comes in from the fact that the pinned 1 layer is antiparallel to pinned

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  AP spin valve with improved signal using Si in one pinned layer for improved DR/R and Sheet Resistance

The pinned 1 layer of an AP spin valve adds stability to the structure, but at the cost of lower DR/R. This is partly due to simple shunting--the extra layer pulls electrons away from the active layers. A secondary effect comes in from the fact that the pinned 1 layer is antiparallel to pinned
2. Figure 1 shows an AP spin valve in the high resistance state. The free layer is antiparallel to Pinned 2 (the reference layer). However, it is parallel to pinned 1, resulting in a low resistance for electrons travelling between the free layer and pinned 1. This reduces the GMR of the spin valve.

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Figure 1

The effects of this can be quite dramatic. An AP spin valve can have 30% lower DR/R than a comparably made simple spin valve.

In this article we discuss the addition of thin layers of Si to the pinned 1 layer of an AP spin valve, although a similar effect could probably be obtained by doping small amounts of Si uniformly into the pinned layer. This should poison any GMR contribution from that layer. Since the GMR from that layer reduces the overall DR/R, this increases signal overall. A second feature is that the Si should increase the resistance of the layer, reducing current shunting and increasing the signal.

Adding Si to active layers in a spin valve reduces DR/R. This has been especially shown in the case of Si in the Cu spacer layer, where even a few angstroms of Si reduces DR/R from 7% to <1%. The Si additions are very efficient electron scattering sites, so they "poison" the GMR of a layer.

In Figure 2 shows the effect of adding a thin layer of Si inside the AP layers of a spin valve. The basic structure is 30 Ru/40 NiFe/5 CoFe/25 Cu/20 CoFe/7 Ru/10 CoFe/t Si/20 CoFe/80 IrMn/30 Ru. The control sample (no Si) has a GMR value of 5.75%. Small amounts (<8Å) of Si increase the DR/R to 6.1%. Additional Si increases the GMR to 6.4%, and the peak could be higher. This represents an 11% increase over the control sample (5.75% GMR).

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Figure 2 DR/R vs Si content in layer 1

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Si thickness (Å)

Figure 3 shows the data in Figure 2 expanded to exemplify the advantage of the thin Si layers.

Figure 3: DR/R expanded to show the best region

Si in pinned 1 layer of IrMn AP

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C0113C01

130 Ru/40 NiFe/5 CoFe/25 Cu/ 20 CoFe/7 Ru/10 CoFe/t Si/20 CoFe/80 IrMn/30 Ru

% RR/

mjc/bg

IBM Confidential

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Si in pinned 1 layer of IrMn AP

C0113C01

6.4

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