Spin Torque Oscillator Cross-Track Width for HDD Signal Noise
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Solution Overview
Problem
Conventional magnetic recording and reproducing heads face challenges in achieving stable oscillations and suppressing medium noise, such as inter-track and inter-bit interference, which affect the signal-to-noise ratio (SNR) of the reproduction signal.
Innovation Solution
The magnetic recording and reproducing apparatus employs a spin torque oscillator with a specific design where the cross-track direction width of the oscillation layer is larger than double the cross-track direction width of the polarizer layer, and the polarizer layer's width is smaller than the inter-track distance, along with the use of shield layers to reduce inter-bit interference, and an external magnetic field is applied to stabilize oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a pillar type spin torque oscillator is used, then the structure is well-defined, but the oscillation stability is insufficient compared to nanocontact type
Solution Approach 1:
The spin torque oscillator is segmented into distinct functional layers: oscillation layer, spacer layer, and polarizer layer. This segmentation allows each layer to be optimized independently for its specific function while achieving stable oscillation without requiring complex overall structure
Solution Approach 2:
Different regions of the spin torque oscillator are given different properties: the oscillation layer has specific magnetic properties for oscillation, the spacer layer provides isolation, and the polarizer layer provides spin polarization. This local differentiation achieves stable oscillation with simpler overall structure
2Stability of the object's composition
If processing damage is reduced in the oscillation layer, then oscillation stability improves, but manufacturing difficulty increases
Solution Approach 1:
The oscillation layer is processed into a pillar shape before assembling the complete spin torque oscillator. This preliminary shaping ensures that when the layer is later processed into final configuration, minimal additional processing damage occurs, thereby maintaining oscillation stability while achieving manufacturability
Solution Approach 2:
A spacer layer is introduced between the oscillation layer and polarizer layer to cushion and protect the oscillation layer from processing damage during subsequent manufacturing steps, thereby preserving oscillation stability without requiring ultra-precise processing
3Measurement precision
If the cross-track direction width of the oscillation layer is increased, then the SNR improves, but the device size increases
Solution Approach 1:
Instead of increasing the cross-track direction width (horizontal dimension) to improve SNR, the invention optimizes the vertical dimension by controlling the thickness of the oscillation layer and spacer layer. This dimensional transition allows SNR improvement without proportionally increasing the lateral device footprint
4Object-affected harmful factors
If shield layers are added to reduce inter-bit interference, then medium noise is suppressed, but device complexity increases
Solution Approach 1:
A nonmagnetic spacer layer is introduced as an intermediary between the oscillation layer and polarizer layer. This spacer layer acts as a magnetic shield that blocks inter-bit interference from reaching the oscillation layer, thereby suppressing medium noise while adding only minimal structural 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 design achieves stable oscillations and reduces medium noise, thereby enhancing the SNR of the reproduction signal and enabling higher recording densities without the need for complex pinning layers, making it suitable for advanced HDD technologies.
Implementation Method 1
a spin torque oscillator reproducing head using the spin torque oscillator
Implementation Method 2
The spin torque oscillator includes an oscillation layer, a polarizer layer, and a spacer layer provided between the oscillation layer and the polarizer layer
Implementation Method 3
an external magnetic field is applied to stabilize oscillations
Implementation Method 4
the use of shield layers to reduce inter-bit interference
Data Source
AI summary
According to an embodiment, a magnetic recording and reproducing apparatus includes a recording medium and a reproducing head. The recording medium includes a concentric circular plurality of tracks. The reproducing head includes a spin torque oscillator and reproduces information from the recording medium using the spin torque oscillator, the spin torque oscillator including an oscillation layer with a first cross-track direction width, a polarizer layer with a second cross-track direction width, and a spacer layer provided between the oscillation layer and the polarizer layer. The first cross-track direction width is larger than double the second cross-track direction width, and the second cross-track direction width is smaller than an inter-track distance.