Tunneling Magnetoresistive Element Free Magnetic Layer Design
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Solution Overview
Problem
Existing tunneling magnetoresistive elements fail to achieve a high rate of resistance change (ΔR/R) due to limitations in their structural design, particularly with layered ferri structures that lead to Barkhausen noise and high coercive force, which affect read characteristics.
Innovation Solution
A tunneling magnetoresistive element with a free magnetic layer comprising soft magnetic sublayers separated by a nonmagnetic metal sublayer and an enhancement sublayer, optimized with a Ti—Mg—O or Ti—O insulating barrier layer, where the nonmagnetic metal sublayer is thin to maintain magnetic coupling and reduce coercive force, and the absence of a layered ferri structure minimizes noise and enhances stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a layered ferri structure is used in the free magnetic layer, then exchange coupling is enhanced, but Barkhausen noise increases and coercive force becomes too large
Solution Approach 1:
The patent removes the layered ferri structure from the free magnetic layer, extracting the source of Barkhausen noise and high coercive force while maintaining exchange coupling through alternative means via the enhancement sublayer with high spin polarizability
Solution Approach 2:
The patent changes the magnetic parameters by eliminating the layered ferri structure and introducing an enhancement sublayer with high spin polarizability, thereby reducing coercive force and Barkhausen noise while maintaining adequate exchange coupling
2Strength
If a layered ferri structure is used in the free magnetic layer, then exchange coupling is enhanced, but the rate of resistance change (ΔR/R) cannot be consistently high
Solution Approach 1:
The patent extracts the layered ferri structure that prevents consistent high ΔR/R performance and replaces it with a simplified structure using an enhancement sublayer, achieving both adequate exchange coupling and consistently high resistance change rate
3Strength
If soft magnetic sublayers are separated by a nonmagnetic metal sublayer, then magnetic coupling is maintained with reduced coercive force, but the structure complexity increases
Solution Approach 1:
The patent applies local quality by introducing a nonmagnetic metal sublayer with specific thickness (1-4 angstroms) at a critical location within the free magnetic layer, creating localized magnetic coupling while maintaining overall structural simplicity and reducing coercive force
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 achieves a consistently high rate of resistance change (ΔR/R) while reducing Barkhausen noise and coercive force, resulting in stable read characteristics and improved performance.
Implementation Method 1
Tunneling magnetoresistive (TMR) elements generate a resistance change by utilizing a tunneling effect
Implementation Method 2
an enhancement sublayer disposed between a first soft magnetic sublayer and the insulating barrier layer and having a spin polarizability higher than those of the soft magnetic sublayers
Implementation Method 3
The soft magnetic sublayers are magnetically coupled to each other and thereby have the same magnetization direction
Data Source
AI summary
A tunnel magnetoresistive element includes a laminate including a pinned magnetic layer, an insulating barrier layer, and a free magnetic layer. The insulating barrier layer is composed of Ti—Mg—O or Ti—O. The free magnetic layer includes an enhancement sublayer, a first soft magnetic sublayer, a nonmagnetic metal sublayer, and a second soft magnetic sublayer. For example, the enhancement sublayer is composed of Co—Fe, the first soft magnetic sublayer and the second soft magnetic sublayer are composed of Ni—Fe, and the nonmagnetic metal sublayer is composed of Ta. The total thickness of the average thickness of the enhancement sublayer and the average thickness of the first soft magnetic sublayer is in the range of 25 to 80 angstroms. Accordingly, the tunneling magnetoresistive element can consistently have a higher rate of resistance change than before.