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Magneto-resistive sensor with in-plane edge junction

IP.com Disclosure Number: IPCOM000016663D
Publication Date: 2003-Jul-08

Publishing Venue

The IP.com Prior Art Database

Abstract

A magnetoresistive sensor structure is proposed which divides the conventional current-in-plane (CIP) sensor structure into two parts and places the two parts side by side rather than on top of each other, effectively reducing the stack height. In this design the film thickness will define one dimension of the junction between pinned and free layer.

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Magneto-resistive sensor with in-plane edge junction

  The steadily increasing areal recording densities require giant magnetoresistive (GMR) sensors with narrower trackwidths as well as narrower shield-to-shield spacing. The 100 Gbit/in2 design, for example, requires a 70 nm trackwidth and 50 nm shield-to-shield spacing, figures which push the envelope of what is currently achievable in manufacturing. On the one hand, reducing the shield-to-shield spacing is mainly a materials issue, since pinning layers such as PtMn already require a minimum thickness of approx. 20 nm to be antiferromagnetic. Other pinning materials have similar thickness limitations. The thickness constraint has already lead to the development of self-pinned sensors, which stabilize the pinned layer via magnetostriction rather than exchange biasing. Defining a narrow trackwidth on the other hand is a lithographic challenge, since 70 nm already requires advanced techniques, such as e-beam lithography or phase shift DUV masks.

What is needed is a novel sensor that can be built with reduced stack height and/or narrow track-width.

Such a sensor is proposed in a first embodiment. The sensor can be built in two different fashions, with the free layer on the top, or the bottom. The current flows in a CIP mode, but the GMR effect will be more like that found in current-perpendicular-to-the-plane (CPP) sensors. GMR multilayers in CPP mode exhibit about twice as large a GMR amplitude as those in current in-plane (CIP) mode. Spin-valves are also predicted to possess higher GMR ratios in CPP mode, making this the preferred mode for optimal sensor operation.

In the second embodiment, a sensor is proposed where the junction itself will define the trackwidth. In this way, ultra-narrow trackwidths on the order of 20-40 nm can be achieved. A novel aspect of this embodiment is that the track-width is defined by a deposited layer thickness rather than lithographically.

In the third embodiment it is proposed how this novel structure for a magnetic memory cell and magnetic memory cell arrays can be utilized.

In all embodiments the GMR spacer layer may also be replaced by an insulating barrier layer. This would not change the conceptual functionality of the devices; however the tunnel- rather than the giant-magneto-resistance effect will be utilized. Moreover the resistance of the devices will increase about 3-6 orders of magnitude.

Figure 1 shows a prior art GMR spin valve sensor. It typically comprises an underlayer, 001, an antiferromagnetic layer, 002, a pinned layer, 003, a spacer layer, 004, a free layer, 005, and a capping layer, 006. The free layer magnetization is in the drawing plane as indicated by the arrow with tips at both ends, while the pinned layer magnetization is perpendicular to the drawing plane as indicated. In a CPP sensor current flows perpendicular to the plane through layers 001, 002, 003, 004, 005, and 006. In a CIP sensor current flows parallel to the plan...