Non-Localized Multi-Free-Layer Spin Valve Reader With SOT Injection
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Solution Overview
Problem
Existing magnetic recording heads, particularly those using non-localized spin valve (NLSV) designs, suffer from limited spin injection efficiency due to a spin polarization of less than 1, resulting in poor signal output and reduced data reading accuracy.
Innovation Solution
The magnetic recording head incorporates a read head design with first and second sensors at the media facing surface, each paired with a spin orbit torque (SOT) spin generator recessed from the surface, utilizing BiSb SOT layers to inject spin current through non-magnetic layers to enhance signal detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a non-localized spin valve (NLSV) design with a pinned layer is used, then the read head can detect magnetic signals, but the spin injection efficiency is limited due to spin polarization less than 1, resulting in poor signal output
Solution Approach 1:
The patent changes the fundamental parameter of spin injection mechanism from traditional pinned layer spin valve to spin orbit torque (SOT) based injection. By using SOT layers with high spin-orbit coupling materials, the spin polarization is enhanced beyond the limitation of conventional pinned layers, directly addressing the spin injection efficiency problem while maintaining signal detection capability
Solution Approach 2:
The patent replaces the conventional pinned layer magnetic field-based spin injection mechanism with an electric current-based SOT mechanism. This substitution eliminates the spin polarization limitation inherent in pinned layers by using spin-orbit coupling effects in heavy metal layers, thereby improving both spin injection efficiency and signal output
2Measurement precision
If the read head uses traditional spin valve structures, then it can read data, but the signal strength is weak due to low spin current injection
Solution Approach 1:
The patent modifies the spin current generation mechanism by introducing SOT layers with high spin-orbit coupling constants. This parameter change enables stronger spin current injection into the sensor layers, directly increasing signal strength while improving data reading accuracy through enhanced spin polarization
Solution Approach 2:
The patent employs composite material structures combining heavy metal SOT layers (such as Pt, Ta, or W) with ferromagnetic sensor layers. This composite approach leverages the high spin-orbit coupling of the heavy metal layer to generate strong spin currents that inject into the ferromagnetic layers, thereby amplifying the read signal while maintaining accurate data detection
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 design significantly improves signal output by enabling efficient spin current injection, enhancing the read head's ability to accurately read data with higher signal strength.
Implementation Method 1
The first and second spin generators each individually comprises at least one spin orbit torque (SOT) layer
Implementation Method 2
there have been various read head designs proposed to boost linear density based on different physical mechanisms such as a tunneling magneto-resistive (TMR) effect
Implementation Method 3
a magneto-resistance (GMR) effect
Data Source
AI summary
The present disclosure generally relates to a magnetic recording head comprising a read head. The read head comprises a first sensor disposed at a media facing surface (MFS) comprising at least one free layer, a second sensor disposed at the MFS comprising at least one free layer, a first spin generator spaced from the first sensor and recessed from the MFS, and a second spin generator spaced from the second sensor and recessed from the MFS. The first and second spin generators each individually comprises at least one spin orbit torque (SOT) layer. The SOT layer may comprise BiSb. The first and second sensors are configured to detect a read signal using a first voltage lead and a second voltage lead. The first and second spin generators are configured to inject spin current through non-magnetic layers to the first and second sensors using a plurality of current leads.