Magnetoresistive Element with Adjustable Magnetostriction
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Solution Overview
Problem
Magnetic tunnel junctions with positive magnetostriction constants face issues due to mechanical stress-induced changes in magnetic properties, leading to high error rates in MRAM devices and decreased sensitivity in sensors, along with poor yield and property dispersion across devices.
Innovation Solution
A magnetoresistive element with a compensating ferromagnetic layer having a different magnetostriction, adjusted in thickness to achieve a net magnetostriction between -10 ppm and +10 ppm, and a ferromagnetic coupling layer for enhanced exchange coupling, which mitigates stress-induced effects and improves magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ferromagnetic layers with positive magnetostriction constant are used, then good electrical and magnetic properties are achieved, but mechanical stress induces changes in magnetic properties leading to high error rates and decreased sensitivity
Solution Approach 1:
A compensating ferromagnetic layer with negative magnetostriction is introduced to counterbalance the positive magnetostriction of the storage and sense layers. This creates a net magnetostriction near zero, compensating for the harmful mechanical stress effects and stabilizing magnetic properties.
Solution Approach 2:
The magnetic tunnel junction is structured as a composite system comprising multiple ferromagnetic layers with different magnetostriction constants (positive and negative) combined in a specific configuration. This composite structure enables cancellation of magnetostriction effects while maintaining good electrical and magnetic properties.
2Reliability
If ferromagnetic layers with positive magnetostriction are used, then good electrical and magnetic properties are achieved, but property dispersion among devices increases resulting in poor yield
Solution Approach 1:
The compensating layer with negative magnetostriction counterbalances the positive magnetostriction of other layers, making the net magnetostriction insensitive to manufacturing variations. This reduces property dispersion across devices and improves yield.
Solution Approach 2:
By adjusting the thickness of the compensating ferromagnetic layer, the net magnetostriction is precisely controlled to be near zero. This parameter optimization minimizes property dispersion and ensures consistent device performance across production batches.
3Object-affected harmful factors
If ferromagnetic layers with negative magnetostriction are used, then mechanical stress effects are reduced, but electrical and magnetic properties deteriorate with low TMR and low exchange bias
Solution Approach 1:
The structure combines ferromagnetic layers with negative magnetostriction (for stress resistance) with layers providing good electrical and magnetic properties. The compensating layer approach allows utilizing negative magnetostriction materials without suffering from their inherent property limitations.
Solution Approach 2:
Different regions of the magnetic tunnel junction are assigned different magnetostriction characteristics: the compensating layer has negative magnetostriction to resist stress, while the storage and sense layers maintain their positive magnetostriction for optimal electrical and magnetic performance. Each layer performs its specialized 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 solution stabilizes magnetic properties, reducing stress-induced errors and sensitivity issues, and minimizes property dispersion across devices, enhancing the performance and reliability of magnetic devices like MRAM and sensors.
Implementation Method 1
the thickness of the compensating ferromagnetic layer is such that the second magnetostriction of the compensating ferromagnetic layer compensates the first storage magnetostriction and/or the first sense magnetostriction, so that a net magnetostriction of the storage layer and/or sense layer is between -10 ppm and +10 ppm
Implementation Method 2
The ferromagnetic coupling layer is adapted for providing an exchange coupling greater than 0.05 erg/cm2
Implementation Method 3
Magnetic tunnel junctions are conventionally made of an insulating barrier, or tunnel barrier, comprising MgO or AlO. The tunnel barrier is sandwiched between two ferromagnetic layers
Data Source
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AI summary
The present disclosure concerns a magnetoresistive element (1) comprising: a storage layer (21) having a first storage magnetostriction; a sense layer (23) having a first sense magnetostriction; a barrier layer (22) between and in contact with the storage and sense layer (21, 23); wherein the magnetoresistive element (1) further comprises a compensating ferromagnetic layer (25) having a second magnetostriction different from the first storage magnetostriction and/or sense magnetostriction, and adapted to compensate the first storage magnetostriction and/or the first sense magnetostriction so that a net magnetostriction of the storage layer (21) and/or sense layer (23) is adjustable between -10 ppm et +10 ppm or more negative than -10 ppm by adjusting a thickness of the compensating ferromagnetic layer (25). The present disclosure concerns also concerns a magnetic device comprising the magnetoresistive element.