Dual Free Layer Magnetic Elements With Amorphous Inserts for Stable TMR
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Solution Overview
Problem
Conventional magnetic read sensors with single free layers and antiferromagnetic pinning structures face challenges in achieving high recording densities due to degraded magnetic pinning layer properties, thermal stability, and exchange bias, leading to reduced process performance and areal recording density.
Innovation Solution
The implementation of dual free layer structures with amorphous insertion layers, such as CoHf, which have a recrystallization temperature of about 300° C. or above, providing enhanced magnetic moment, TMR signal, and thermal stability without increasing coercivity and magnetostriction, and featuring high-quality, smooth interfaces for improved sensor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional single free layer structures with antiferromagnetic pinning structures are used, then the device structure is simple, but the thermal stability and exchange bias are degraded, leading to reduced recording density
Solution Approach 1:
The patent divides the free layer into two separate free layers (first free layer and second free layer) with a barrier layer between them. Each free layer can be independently optimized for magnetic properties, allowing improved thermal stability and exchange bias while maintaining manageable device complexity through modular design
Solution Approach 2:
The patent employs composite material structures by combining different ferromagnetic materials (CoFeB, CoFeTaB) with amorphous insertion layers (Ta, W) and antiferromagnetic pinning layers. This composite approach enables simultaneous optimization of thermal stability, magnetic moment, and exchange bias properties that cannot be achieved with single-material structures
2Quantity of substance
If the width and pitch of write tracks are narrowed to achieve higher recording densities, then the recording density increases, but the magnetic pinning layer properties and thermal stability are degraded
Solution Approach 1:
The patent applies local quality optimization by introducing amorphous insertion layers (Ta, W) specifically at the interfaces between ferromagnetic layers and pinning layers. These localized amorphous regions provide enhanced magnetic pinning properties and thermal stability precisely where needed, allowing narrow track widths to be maintained without degrading magnetic performance
Solution Approach 2:
The patent changes material parameters by using amorphous insertion layers with specific recrystallization temperatures and magnetic properties. These parameter changes in the insertion layers enhance the exchange bias and thermal stability, enabling higher recording densities to be achieved while maintaining reliable magnetic pinning
3Ease of manufacture
If amorphous insertion layers with low recrystallization temperature are used, then the manufacturing process is easier, but the thermal stability is reduced
Solution Approach 1:
The patent selects amorphous insertion layers (Ta, W) with specifically high recrystallization temperatures (above 300°C) to maintain thermal stability during manufacturing and operation. This parameter selection enables both ease of manufacture through amorphous material deposition and thermal stability through high recrystallization temperature, resolving the contradiction between processing ease and thermal performance
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 dual free layer structures with amorphous insertion layers achieve higher TMR signals, increased thermal stability, and reduced noise, resulting in improved signal-to-noise ratio and process controllability, contributing to enhanced recording density and device reliability.
Implementation Method 1
Each of the first and second amorphous insertion layers independently has a recrystallization temperature of about 300° C. and above
Implementation Method 2
tunnel magnetoresistive (TMR) reader sensors
Data Source
AI summary
A magnetic element includes a first free layer, a barrier layer over the first free layer, and a second free layer over the barrier layer. The first free layer includes a first ferromagnetic bilayer and a first amorphous insertion layer (e.g., CoHf) between the first ferromagnetic bilayer. The first ferromagnetic bilayer is selected from CoB, CoFeB, FeB, and combinations thereof. The second free layer includes a second ferromagnetic bilayer and a second amorphous insertion layer (e.g., CoHf) between the second ferromagnetic bilayer. The second ferromagnetic bilayer is selected from CoB, CoFeB, FeB, and combinations thereof. Each of the first and the second amorphous insertion layer independently can be ferromagnetic or non-ferromagnetic and can have a recrystallization temperature of about 300° C. and above. The magnetic element can further include a non-ferromagnetic amorphous buffer layer and/or a non-ferromagnetic amorphous capping layer. The magnetic element can further include a ferromagnetic amorphous seed layer.