CPP Magnetic Read Head Elongated Pinned Layer Design
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Solution Overview
Problem
Current CPP GMR magnetic read heads face challenges with low signal amplitude due to limited spin interaction length and high parasitic resistance, which restricts their effectiveness in high-density magnetic recording applications.
Innovation Solution
The solution involves elongating the pinned and pinning layers by 0.05 microns and adding a conductive layer to divert current away from the bottom magnetic shield, increasing spin interaction distance and reducing parasitic resistance by bypassing the AFM layer, while maintaining a small shield-to-shield spacing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pinned layer and pinning layer are elongated to increase spin interaction length, then signal amplitude is improved, but device thickness increases
Solution Approach 1:
The patent transitions from a conventional planar GMR stack to a three-dimensional structure by elongating the pinned layer and pinning layer in the vertical dimension. This dimensional change allows increased spin interaction length without proportionally increasing the horizontal footprint, thereby improving signal amplitude while controlling overall device thickness.
Solution Approach 2:
The conductive layer is nested within the elongated pinned layer structure, filling the space between the pinned layer and the top magnetic shield. This nesting approach maximizes the use of vertical space, allowing the pinned layer to be elongated for increased spin interaction while the conductive layer occupies the remaining space without further increasing device thickness.
2Reliability
If a conductive layer is added to divert current away from the bottom magnetic shield, then parasitic resistance is reduced, but device complexity increases
Solution Approach 1:
The conductive layer is extracted and positioned specifically at the location where parasitic resistance is most problematic - between the pinned layer and the top magnetic shield. By strategically placing the conductive layer only where needed, the patent reduces parasitic resistance without requiring a complete redesign of the entire device structure.
Solution Approach 2:
The conductive layer serves multiple functions simultaneously: it acts as a current diversion path to reduce parasitic resistance, provides a magnetic shield for the elongated pinned layer, and maintains electrical connectivity. This multi-functionality reduces the need for separate components, thereby limiting the increase in device complexity.
3Productivity
If the shield-to-shield spacing is kept small to maintain high recording density, then productivity is improved, but parasitic resistance increases
Solution Approach 1:
The conductive layer acts as an intermediary element between the bottom magnetic shield and the top magnetic shield. It provides a low-resistance current path that mediates the electrical connection, allowing the shields to be positioned close together for high recording density while the conductive layer prevents parasitic resistance from increasing due to the reduced spacing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances the signal amplitude by increasing the spin interaction length and reducing total resistance, thereby improving the signal-to-noise ratio and enabling higher recording densities without scaling down signal amplitude.
Implementation Method 1
the resistance increase (known as Giant Magneto-Resistance or GMR) derives from the fact that electrons in a magnetized solid are subject to significantly less scattering by the lattice when their own magnetization vectors (due to spin) are parallel (as opposed to anti-parallel) to the direction of magnetization of their environment
Implementation Method 2
adding a conductive layer to divert current away from the bottom magnetic shield, increasing spin interaction distance and reducing parasitic resistance by bypassing the AFM layer
Data Source
AI summary
CPP magnetic read head designs have been improved by increasing the length of the AFM layer relative to that of both the free and spacer layers. The length of the pinned layer is also increased, but by a lesser amount, an abutting conductive layer being inserted to fill the remaining space over the AFM layer. The extended pinned layer increases the probability of spin interaction while the added conducting layer serves to divert sensor current away from the bottom magnetic shield which now is no longer needed for use as a lead.