SOT Differential Reader for High Density Storage
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Solution Overview
Problem
Existing read heads face challenges in achieving higher recording densities without reducing the shield-to-shield spacing, and conventional read sensors suffer from unsymmetrical responses due to different spin hall angle properties.
Innovation Solution
The proposed spin-orbital torque (SOT) differential reader design includes a multi-terminal device with specific layers such as silicide seed multilayers, spin hall effect layers, interlayers, and free layers, which improve reader resolution without decreasing the shield-to-shield spacing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional read sensors are minimized to reduce size, then the sensor dimensions are reduced to about 25 nm, but the shield-to-shield spacing cannot be decreased further
Solution Approach 1:
The read sensor is divided into two separate read heads positioned side-by-side between the shields. Each read head contains its own spin hall effect layer and associated structures. This segmentation allows the sensor functionality to be distributed across multiple elements, improving resolution through differential measurement while maintaining the same shield-to-shield spacing.
Solution Approach 2:
Instead of reducing the shield-to-shield spacing in the vertical dimension, the invention extends the sensor array in the lateral dimension by placing two read heads adjacent to each other. This dimensional transition allows resolution improvement without further minimizing the already-constrained vertical spacing between shields.
2Measurement precision
If differential reader configurations are used to improve reader resolution, then reader resolution is improved, but unsymmetrical response occurs due to different spin hall angle properties
Solution Approach 1:
Each read head in the differential configuration is equipped with spin hall effect layers having specifically engineered local properties. The spin hall angles are designed to be substantially equal in magnitude but opposite in sign between the two read heads, creating locally optimized conditions that produce symmetrical differential responses when reading opposite magnetic polarities.
Solution Approach 2:
The invention deliberately introduces controlled asymmetry in the form of spin hall effect layers with opposite spin hall angles in the two read heads. This asymmetric design is purposeful and creates symmetric differential output signals, as the opposite spin hall angles compensate for each other in the differential measurement, eliminating baseline shifts and improving measurement symmetry.
3Adaptability or versatility
If materials with different spin hall angle properties are used in read sensors, then the read sensor response varies, but this causes baseline shift in differential reader configurations
Solution Approach 1:
The invention changes the critical parameter of spin hall angle from being different between read heads to being substantially equal in magnitude and opposite in sign. This parameter transformation is achieved through careful selection and engineering of the spin hall effect layer materials and structures, ensuring that the differential reader produces stable baseline responses without shifts while maintaining adaptable sensor response to magnetic signals.
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 SOT differential reader enhances reader resolution and maintains the shield-to-shield spacing, addressing the limitations of conventional read sensors and enabling higher recording densities.
Implementation Method 1
a first spin hall effect layer disposed over the silicide seed multilayer, the first spin hall effect layer comprising BiSb or an alloy thereof having a crystalline structure of (012)
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
The present disclosure generally relates to spin-orbital torque (SOT) differential reader designs. The SOT differential reader is a multi-terminal device comprising a first seed layer, a first spin hall effect (SHE) layer, a first interlayer, a first free layer, a gap layer, a second seed layer, a second SHE layer, a second free layer, and a second interlayer. The gap layer is disposed between the first SHE layer and the second SHE layer. The materials and dimensions used for the first and second seed layers, the first and second interlayers, and the first and second SHE layers affect the resulting spin hall voltage converted from spin current injected from the first free layer and the second free layer, as well as the ability to tune the first and second SHE layers. Moreover, the SOT differential reader improves reader resolution without decreasing the shield-to-shield spacing (i.e., read-gap).