Tunneling Magnetic Sensor Mg Protective Layer Low Magnetostriction
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Solution Overview
Problem
Conventional tunneling magnetic sensors face challenges in achieving a balance between low magnetostriction and a large change in reluctance, which affects the sensitivity and stability of reproducing heads in magnetic storage devices.
Innovation Solution
A tunneling magnetic sensor is designed with a free magnetic layer having low magnetostriction, utilizing a first protective layer made of magnesium (Mg) and a second protective layer of tantalum (Ta), along with a Co—Fe alloy enhancement sublayer and a Ni—Fe alloy soft magnetic sublayer, to enhance the change in reluctance without increasing magnetostriction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the Fe content of alloys (Ni-Fe, Co-Fe, Ni-Co-Fe) is increased to increase spin polarizability and change in reluctance, then the change in reluctance increases, but the magnetostriction increases causing noise and low stability
Solution Approach 1:
The patent changes the material composition parameters by using a Co-Fe-B alloy with specific proportions (Co: 5-30 at%, Fe: 50-70 at%, B: 5-20 at%) to achieve low magnetostriction while maintaining high spin polarizability. This parameter optimization resolves the contradiction by finding the optimal composition range that satisfies both requirements
Solution Approach 2:
The patent creates a composite magnetic layer structure combining Co-Fe-B alloy with specific properties (low magnetostriction, high spin polarizability) to achieve both large change in reluctance and low noise. The composite nature of the alloy with multiple elements working together resolves the contradiction between sensitivity and stability
2Measurement precision
If conventional materials are used for the free magnetic layer, then the structure is simple, but the change in reluctance is insufficient
Solution Approach 1:
The patent divides the magnetic layer into multiple functional sublayers: a Co-Fe-B alloy layer for low magnetostriction, an enhancement layer for spin polarizability, and a soft magnetic layer for magnetic properties. This segmentation allows each layer to optimize its function, achieving large change in reluctance while managing complexity through functional decomposition
Solution Approach 2:
Different regions of the magnetic layer structure are assigned different material compositions and properties: the Co-Fe-B layer provides low magnetostriction, the enhancement layer provides high spin polarizability, and the soft magnetic layer provides favorable magnetic characteristics. This local quality differentiation resolves the contradiction by allowing each region to be optimized for its specific function
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 sensor achieves a larger change in reluctance compared to conventional sensors while maintaining low magnetostriction, thereby improving detection sensitivity and stability.
Implementation Method 1
A tunneling magnetic sensor (tunneling magnetoresistive element) causes a change in reluctance using tunnel effect
Implementation Method 2
Ferromagnetic materials, such as iron (Fe), nickel (Ni), and cobalt (Co), for forming the pinned and free magnetic layers of the tunneling magnetic sensors have slight distortion (magnetostriction) if the ferromagnetic materials are magnetized
Data Source
AI summary
A tunneling magnetic sensor includes a pinned magnetic layer of which the magnetization is pinned in one direction, an insulating barrier layer, and a free magnetic layer of which the magnetization is varied by an external magnetic field, these layers being arranged in that order from the bottom. A first protective layer made of magnesium (Mg) is disposed on the free magnetic layer. The tunneling magnetic sensor has a larger change in reluctance as compared to conventional magnetic sensors including no first protective layers or including first protective layers made of Al, Ti, Cu, or an Ir—Mn alloy. The free magnetic layer has lower magnetostriction as compared to free magnetic layers included in the conventional magnetic sensors.