ISHE Spintronic Reader for Shorter Shield-to-Shield Spacing
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Solution Overview
Problem
Existing hard disk drives face challenges in reducing the read gap length without compromising the amplitude and noise of the readout signal, as conventional TMR readers require a reference layer and have a thickness that is difficult to further reduce.
Innovation Solution
Implementing a spintronic reader design based on the Inverse Spin Hall Effect (ISHE) that converts a longitudinal spin-current into a transversal charge current, utilizing a sense layer with magnetization biased in the cross-track direction, a spin-orbit layer with a large spin hall angle, and an electrical contact layer, eliminating the need for a reference layer and reducing the overall stack thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional TMR readers are used, then the readout signal amplitude and noise performance are maintained, but the shield-to-shield spacing and overall stack thickness cannot be reduced further
Solution Approach 1:
The reference layer is extracted and removed from the reader stack. Instead of using a conventional TMR structure with both sense and reference layers, the invention uses only a sense layer with perpendicular magnetization, eliminating the need for a reference layer while maintaining readout functionality through the ISHE effect.
Solution Approach 2:
The invention changes the fundamental operating principle from TMR (tunnel magnetoresistance) to ISHE (inverse spin Hall effect). This parameter change allows the reader to function with a simplified stack structure, achieving reduced shield-to-shield spacing while maintaining signal quality through spin-orbit coupling in the sense layer.
2Productivity
If the reader stack thickness is reduced, then the data density and KFCI capability are improved, but the conventional TMR reader structure cannot achieve further reduction
Solution Approach 1:
The reference layer is extracted and removed from the reader stack. Instead of using a conventional TMR structure with both sense and reference layers, the invention uses only a sense layer with perpendicular magnetization, eliminating the need for a reference layer while maintaining readout functionality through the ISHE effect.
Solution Approach 2:
The sense layer is constructed using composite material structures with specific perpendicular magnetization characteristics, such as CoFeB/MgO/CoFeB sandwiches or CoFeB/CoFe sandwiches. These composite structures enable the ISHE effect to operate efficiently with reduced thickness while maintaining the necessary magnetic and electrical properties.
3Manufacturing precision
If the sense layer length in cross-track direction is reduced, then the resolution and data capacity are improved, but the electrical contact and current flow become problematic
Solution Approach 1:
The invention changes the current flow direction from in-plane to perpendicular-to-plane (CPP) configuration. By applying current perpendicular to the reader stack and utilizing the ISHE effect, the system generates a transverse voltage signal that can be measured with contacts positioned at the edges of the sense layer, enabling read gap reduction without compromising electrical contact.
Solution Approach 2:
The invention replaces the conventional in-plane current flow mechanism with a perpendicular current flow mechanism that exploits spin-orbit coupling. This substitution allows the generation of transverse voltage signals through the ISHE effect, enabling edge-contact configurations with reduced read gap length.
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 ISHE-based reader achieves a significantly shorter shield-to-shield spacing, increasing the maximum KFCI capability by a factor of 2 compared to TMR readers, with a total thickness of 6-12 nm, allowing for improved data density and reduced thermal fluctuations.
Implementation Method 1
ISHE can convert a longitudinal spin-current into a transversal charge current where a spin-current can be created by flowing a charge current in the perpendicular to plane direction (CPP current) through a sense magnetic layer adjacent to the material with spin orbit interactions
Implementation Method 2
a spin-current can be created by flowing a charge current in the perpendicular to plane direction (CPP current) through a sense magnetic layer adjacent to the material with spin orbit interactions
Data Source
AI summary
The present embodiments relate to reader designs that incorporate Inverse Spin Hall Effect (ISHE). ISHE can convert part of a longitudinal spin-current into a transversal charge current where a spin-current can be created by flowing a charge current in the perpendicular to plane direction (CPP current) through a sense magnetic layer adjacent to the material with spin orbit interactions. The spintronic reader can include a stack of layers that includes a sense layer with a magnetization configured to be biased primarily in a cross-track direction relative to an air-bearing surface (ABS), a spin-orbit layer characterized by a spin hall angle, and an electrical contact layer disposed adjacent to the spin-orbit layer to enable a current to flow throughout the sense layer and spin orbit layer.