Magnetoresistive Element Spin Filter Layer Crystallinity
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Solution Overview
Problem
The existing magnetoresistive effect elements, particularly of the CPP type, face challenges in achieving high magnetoresistive changing ratios due to deteriorated crystallinity caused by the insertion of insulating layers, which affects spin-dependent interface scattering, bulk scattering, and spin diffusion length, leading to reduced magnetic performance.
Innovation Solution
Incorporating a spin filter layer made of nonmagnetic metal between the free layer and the protecting layer to improve crystallinity and enhance the magnetoresistive effect, with a thickness range of 5 nm to 20 nm, which increases the resistance and magnetoresistive effect by improving spin-dependent scattering and bulk scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a resistance increasing layer including an insulator is inserted into the spin valve film to improve the magnetoresistive effect, then the magnetoresistive changing ratio is improved, but the crystallinity of the film is deteriorated
Solution Approach 1:
A spin filter layer made of nonmagnetic metal is introduced as an intermediary between the resistance increasing layer and the free layer. This intermediary layer has dual functionality: it maintains the high resistance necessary for large magnetoresistive effect while simultaneously providing a crystalline structure that improves or maintains the overall film crystallinity, thereby resolving the contradiction between improving MR and maintaining crystallinity
Solution Approach 2:
The patent creates a composite structure combining the resistance increasing layer (with insulator) and the spin filter layer (nonmagnetic metal) to form a layered composite. This composite structure leverages the high resistance property of the insulator layer while the metal layer contributes to crystallinity, achieving both improved magnetoresistive effect and maintained crystallinity simultaneously
2Quantity of substance
If the total film thickness of spin-depending layer is made very thin to reduce resistance, then the resistance is reduced, but the number of interfaces is reduced leading to small output absolute value
Solution Approach 1:
The spin filter layer is selectively positioned adjacent to the free layer where spin-dependent scattering is most critical. This local placement optimizes the scattering effect at the most important interface while keeping the overall film thickness thin, thereby maintaining low resistance while maximizing output through enhanced spin-dependent scattering at the critical location
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 configuration results in a magnetic head with high sensitivity and large output, capable of stable magnetic detection at high recording densities, and contributes to the development of highly integrated magnetic memory systems.
Implementation Method 1
an element that has a multilayer film of the sandwich structure of a ferromagnetic layer/nonmagnetic layer/ferromagnetic layer wherein a ferromagnetic layer is not antiferromagnetically coupled. Namely, magnetization is pinned by applying an exchange bias magnetic field to one (called 'a pinned layer' or 'a magnetization pinned layer') of two ferromagnetic layers nipping a nonmagnetic layer (called 'a spacer layer' or 'an intermediate layer'), while the other ferromagnetic layer (called 'a free layer' or 'a magnetization free layer') is inverted in the magnetization by an external magnetic field (signal magnetic field). Thus, the large magnetoresistive effect is obtained by changing the relative angle of magnetizing directions between the two ferromagnetic layers arranged such that the nonmagnetic layer is disposed therebetween.
Implementation Method 2
the spin valve includes a portion (pinned layer/spacer layer/free layer) for spin-dependently scattering an electron and a portion (a buffer layer, an antiferromagnetic layer, a protecting layer, etc.) having small spin-dependent scattering. When the former resistance is expressed as Rsd and the latter resistance is expressed as Rsi, the MR of the spin valve can be shown as MR=ΔRsd/(Rsi+Rsd).
Data Source
AI summary
A magnetoresistive effect element includes a magnetization pinned layer, a magnetization free layer; a nonmagnetic metal layer disposed between the magnetization pinned layer and the magnetization free layer, a resistance increasing layer, a spin filter layer, and a pair of electrodes. The resistance increasing layer includes a insulation portion and is disposed in at least one of the magnetization pinned layer, the magnetization free layer, and the nonmagnetic metal layer. The spin filter layer is disposed to be adjacent to the magnetization free layer and has a thickness in a range of 5 nm to 20 nm. The magnetization free layer is disposed between the spin filter layer and the nonmagnetic metal layer. The magnetization pinned layer, the magnetization free layer, the nonmagnetic layer, the resistance increasing layer, and the spin filter layer are disposed between the electrodes.