TMR Sensor Pinned Layer Sub-layering for Barrier Smoothness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetoresistive sensors face performance issues due to roughness of the barrier layer, which increases coupling between pinned layers and free layers, and potential thermal instability, limiting the thinness of the barrier layer and affecting recording areal densities.
Innovation Solution
A top TMR stack configuration with a tantalum-containing separation layer between antiparallel coupled pinned layers, improving antiparallel coupling strength and reducing interlayer coupling, while maintaining smoothness of the barrier layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the barrier layer is made thinner to improve sensor performance, then the coupling between pinned layers and free layers increases, but the barrier layer roughness worsens
Solution Approach 1:
A separation layer is introduced between the pinned layers and the barrier layer. This intermediary layer acts as a mediator that prevents direct interaction between the pinned layers and the barrier layer, thereby reducing the harmful coupling effect while allowing the barrier layer to maintain its required smoothness for thin barrier layer operation
Solution Approach 2:
The pinned layer structure is segmented into multiple sub-layers (first pinned layer, second pinned layer, and sub-second pinned layer) separated by the separation layer. This segmentation allows each sub-layer to be independently optimized and reduces the overall coupling strength between the pinned structure and the free layer
2Productivity
If the barrier layer is made thinner to increase recording areal density, then the sensor performance improves, but thermal instability increases
Solution Approach 1:
The separation layer serves as a thermal barrier and intermediary structure that protects the thin barrier layer from thermal fluctuations. By introducing this additional layer, thermal stability is improved while maintaining the thin barrier layer configuration necessary for high recording areal density
Solution Approach 2:
The sensor structure employs a composite multi-layer configuration including different magnetic and non-magnetic materials (CoFeB, CoFe, Ru, Ta, MgO) with distinct properties. This composite structure allows optimization of each layer for specific functions including thermal stability, magnetic coupling, and barrier properties
3Strength
If the pinned layers are moved closer to the free layer to enhance pinning strength, then the coupling between layers increases, but the interlayer coupling becomes excessive
Solution Approach 1:
The separation layer acts as a mediator that decouples the magnetic interaction between pinned layers and the free layer. This allows the pinned layers to be positioned closer to the free layer for enhanced pinning strength while the separation layer prevents excessive interlayer coupling by blocking direct magnetic interaction
Solution Approach 2:
The separation layer introduces local quality differentiation in the magnetic coupling profile. It allows strong pinning interaction in the vertical direction (between pinned layers and antiferromagnetic layer) while reducing lateral coupling to the free layer, creating spatially differentiated magnetic interaction strengths
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
Enhances pinning strength, reduces interlayer coupling, and maintains tunneling magnetoresistance coefficients, enabling higher recording areal densities and improved sensor reliability.
Implementation Method 1
The pinned structure includes a first pinned layer exchange coupled to the antiferromagnetic pinning layer, an antiparallel coupling layer, and a second pinned stack disposed between the barrier layer and the antiparallel coupling layer. The second pinned stack antiparallel coupled to the first pinned layer
Implementation Method 2
a magnetoresistive read sensor having a free layer, a barrier layer and a pinned structure between the barrier layer and an antiferromagnetic pinning layer
Implementation Method 3
magnetic flux emanating from a surface of the recording medium causes rotation of a magnetization vector of a sensing or free layer of the MR sensor, which in turn causes the change in resistance
Implementation Method 4
A top TMR stack configuration with a tantalum-containing separation layer between antiparallel coupled pinned layers, improving antiparallel coupling strength and reducing interlayer coupling
Data Source
AI summary
Methods and apparatus provide magnetoresistance sensors. A tunneling magnetoresistance (TMR) sensor may include configurations that are arranged as a top TMR stack. One of two antiparallel layers of pinned layers within the TMR stack may be subdivided by a spacer layer. Tantalum may form the spacer layer that is inserted in a reference layer, which is one of the pinned layers and is located between a barrier layer and an antiparallel coupling layer that enables antiparallel coupling between the reference layer and a keeper layer of the pinned layers. The barrier layer deposited on a free layer of the TMR stacks separates the pinned layers from the free layer such that TMR effects are detectable with the sensors.