Magnetoresistive Element Stress Control via Insertion Layer
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Solution Overview
Problem
Magnetoresistive effect elements, particularly CPP-GMR elements, face challenges in maintaining a stable MR rate of change over time due to internal stress-induced deterioration, which affects their reliability and performance in high-density magnetic recording applications.
Innovation Solution
Incorporating a thin film insertion layer with a stress-matching oxide, nitride, or oxynitride material between the free layer and the cap layer to control internal stress distribution, thereby reducing the impact of current energization-induced heat generation and atom migration, and maintaining the spin-dependent interface scattering effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a spin-valve film structure with thin total film thickness is used to achieve CPP-GMR element fabrication, then the element can be manufactured, but the resistance value becomes very small and the resistance change amount decreases
Solution Approach 1:
The patent employs a composite structure combining metal layers (CoFeB, Ru) with an oxide layer (MgO) to create the spin-valve film. This composite material approach allows the thin film structure needed for CPP-GMR fabrication while the oxide layer provides spin-dependent scattering to maintain adequate resistance values. The specific combination of ferromagnetic metal layers with a nonmagnetic oxide spacer layer creates the necessary conditions for both manufacturability and functional performance.
Solution Approach 2:
The patent introduces a FeCoB layer specifically at the interface with the MgO oxide layer to enhance spin-dependent interface scattering. This local modification of material composition at the critical interface region increases the resistance change amount without requiring overall thickening of the film structure. The FeCoB layer is strategically positioned only where it is needed to maximize the magnetoresistive effect at the spin-dependent scattering interface.
2Reliability
If current is passed perpendicularly through the spin-valve film in CPP-GMR element, then a larger GMR effect is obtained, but internal stress-induced deterioration occurs over time
Solution Approach 1:
The patent introduces a Ru layer as an intermediary between the CoFeB layer and the MgO oxide layer. This Ru intermediary layer serves to reduce internal stress at the interface and prevent atom migration that would otherwise occur under prolonged current energization. The Ru layer acts as a buffer that maintains the structural integrity of the spin-valve film while allowing the CPP-GMR effect to function with high magnitude over time.
Solution Approach 2:
The patent incorporates the Ru layer in advance during fabrication to prevent future stress-induced deterioration. This preemptive measure cushions against the internal stress that will develop when current is passed through the element, preventing atom migration and interface degradation before they can occur. The Ru layer is positioned beforehand to protect the critical CoFeB-MgO interface from stress-related failures during operation.
3Reliability
If Fe50Co50 material is used for pinned and free layers to increase spin-dependent scattering, then interface scattering effect increases, but bulk scattering effect becomes insufficient for 200 Gbpsi performance
Solution Approach 1:
The patent changes the material parameter from conventional CoFe (fcc structure) to CoFeB with specific composition ratios (Co50Fe50 or Co60Fe40) and bcc crystal structure. This parameter change in material composition and crystal structure enhances the spin-dependent interface scattering effect at the CoFeB-MgO interface, providing the necessary scattering strength for high-density recording applications requiring 200 Gbpsi performance.
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
The solution effectively stabilizes the MR rate of change, enhancing the reliability and performance of magnetoresistive effect elements by reducing stress-induced deterioration and maintaining high resistance change values, even under prolonged current energization.
Implementation Method 1
a GMR head including a highly sensitive spin-valve film using a giant magneto-resistance effect (GMR)
Implementation Method 2
In the spin-valve film, a large magnetoresistive effect is obtained by a change in a relative angle of the magnetization directions of the two ferromagnetic layers
Implementation Method 3
reducing the impact of current energization-induced heat generation and atom migration
Data Source
AI summary
A magnetoresistive effect element includes a fixed magnetization layer; a free magnetization layer; a nonmagnetic spacer layer between the fixed magnetization layer and the free magnetization layer; and an insertion layer disposed on an opposite side of the free magnetization layer from the nonmagnetic spacer layer, wherein the first insulating layer has an oxide, a nitride, or an oxynitride including at least one kind of element selected from a group constituted of Al (aluminum), Si (silicon), Mg (magnesium), Ta (tantalum) and Zn (zinc) as a major constituent, and the insertion layer has an oxide, a nitride, or an oxynitride including at least one kind of element selected from a group constituted of Al (aluminum), Si (silicon), Mg (magnesium), Ta (tantalum) and Zn (zinc) as a major constituent.