CPP Magnetoresistive Head Spin Torque Noise Suppression
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Solution Overview
Problem
Current perpendicular to plane magnetoresistive heads experience significant spin torque noise due to the relative angle between the magnetization of the pinned and free layers, which deteriorates the signal-to-noise ratio (SNR) and production yield.
Innovation Solution
The relative angle between the magnetization of the second pinned layer and the free layer is controlled within specific ranges (70 to 80 degrees or 100 to 110 degrees) depending on the direction of the sensing current, and the signal waveform asymmetry is adjusted to optimize the configuration, using a spin valve type magnetoresistive element with a laminated structure and conductive electrodes to apply sensing current perpendicularly to the magnetoresistive film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current perpendicular to plane magnetoresistive head uses a standard spin valve structure with pinned and free layers, then the giant magnetoresistance effect enables high sensitivity detection, but spin torque noise is generated due to the relative angle between magnetization of pinned and free layers, deteriorating the signal-to-noise ratio
Solution Approach 1:
The invention divides the traditional single pinned layer structure into two separate pinned layers (first pinned layer and second pinned layer) with different magnetization directions. The first pinned layer has magnetization in the film plane direction while the second pinned layer has magnetization perpendicular to the film plane. This segmentation allows the sensing current to flow through different magnetic layers with optimized relative angles, reducing spin torque noise while maintaining detection sensitivity through the giant magnetoresistance effect.
Solution Approach 2:
The invention applies different magnetization orientations to different regions of the magnetoresistive element. Specifically, the first pinned layer maintains magnetization in the film plane direction for optimal spin torque noise suppression, while the second pinned layer uses perpendicular magnetization for enhanced detection capability. This local quality differentiation allows each layer to contribute optimally to both noise reduction and signal detection.
2Reliability
If the relative angle between pinned layer and free layer magnetization is optimized to reduce spin torque noise, then the signal-to-noise ratio improves, but the device complexity increases due to the need for multiple pinned layers with different magnetization directions
Solution Approach 1:
The invention merges the functions of noise suppression and signal detection into a single magnetoresistive element by integrating two pinned layers with different magnetization directions. The first pinned layer (in-plane magnetization) primarily suppresses spin torque noise, while the second pinned layer (perpendicular magnetization) enhances detection sensitivity. This merging approach achieves both objectives simultaneously without requiring separate structures, thereby improving reliability while controlling device complexity.
Solution Approach 2:
The magnetoresistive element employs a composite structure combining ferromagnetic layers with different magnetic anisotropy characteristics. The first pinned layer uses materials with in-plane magnetic anisotropy, while the second pinned layer uses materials with perpendicular magnetic anisotropy. This composite material approach enables the element to exhibit both noise suppression and high sensitivity properties through the giant magnetoresistance effect, achieving improved reliability without excessive complexity.
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 effectively suppresses spin torque noise, improves the SNR, and enhances the production yield of magnetic heads by reducing noise incidence and optimizing signal waveform asymmetry.
Implementation Method 1
makes it possible to substantially pin the magnetization of the ferromagnetic layer touching the antiferromagnetic layer through a magnetic exchange coupling field generated at the interface between the antiferromagnetic layer and the ferromagnetic layer
Implementation Method 2
the magnetoresistance effect of a multilayer film formed by laminating ferromagnetic metal layers with a nonmagnetic metal layer in between has become substantial, and the resulting 'giant magnetoresistance effect'
Data Source
AI summary
Embodiments of the present invention aim suppress the generation of spin torque noise in a current perpendicular to plane magnetoresistive head. According to one embodiment, when sensing current is applied to a current perpendicular to plane magnetoresistive head from a free layer toward a first pinned layer, a configuration wherein the relative angle between the magnetization of a second pinned layer and the magnetization of the free layer is in the range of 70 to 80 degrees is used. Further, when sensing current is applied to a current perpendicular to plane magnetoresistive head from a first pinned layer toward a free layer, a configuration wherein the relative angle between the magnetization of a second pinned layer and the magnetization of the free layer is in the range of 100 to 110 degrees is used.