CPP GMR Sensor Synthetic Pinned Layer Magnetoresistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
CPP-GMR sensors face challenges in achieving sufficient magnetoresistance change due to the small resistance contribution from the free, pinned, and non-magnetic spacer layers when current flows perpendicular to the layers, limiting their effectiveness in high-density magnetic storage applications.
Innovation Solution
A CPP magnetoresistive sensor with a synthetic pinned layer structure, where the ratio of the second ferromagnetic layer's thickness to the first ferromagnetic layer's thickness is between 1.4 and 1.9, and the ratio of their saturation magnetization products is between 0.9 and 1.1, enhancing bulk scattering and suppressing effective magnetization to increase magnetoresistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional SV configuration is applied to CPP-GMR sensor, then the sensor structure is simple, but the change in magnetoresistance is insufficient
Solution Approach 1:
The patent divides the pinned layer into multiple ferromagnetic layers (first pinned layer, second pinned layer, third pinned layer) separated by nonmagnetic spacer layers. This segmentation creates multiple interfaces that enhance spin-dependent scattering, thereby increasing the change in magnetoresistance while managing the complexity through a systematic layered structure.
Solution Approach 2:
The patent employs a composite structure combining ferromagnetic layers (CoFeB, CoFe) with nonmagnetic spacer layers (Ru, Cu) and antiferromagnetic layers (IrMn). This composite material approach creates multiple boundaries with different magnetic and nonmagnetic properties, enhancing the overall magnetoresistive effect through cumulative spin scattering at each interface.
2Measurement precision
If the number of boundaries is increased by inserting nonmagnetic spacer layers, then the spin scattering is enhanced, but the device complexity increases
Solution Approach 1:
The patent introduces nonmagnetic spacer layers (Ru, Cu) specifically at the interfaces between ferromagnetic layers to create localized regions of high spin scattering. These spacer layers are strategically positioned where they can maximize the spin-dependent scattering effect without requiring the entire structure to be complex, thus enhancing local quality at critical interfaces.
3Measurement precision
If the thickness ratio of ferromagnetic layers is optimized, then the magnetoresistance change is maximized, but the manufacturing precision requirement increases
Solution Approach 1:
The patent optimizes specific parameters including the thickness of each ferromagnetic layer (5-10 nm for first pinned layer, 3-7 nm for second pinned layer, 2-5 nm for third pinned layer) and the thickness of nonmagnetic spacer layers (0.3-0.8 nm for Ru, 0.5-1.5 nm for Cu). These parameter changes are designed to maximize spin scattering while maintaining manufacturability through well-defined thickness ranges.
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
This configuration enhances the total change in magnetoresistance while maintaining suppressed effective magnetization, improving the sensor's performance in high-density magnetic storage applications.
Implementation Method 1
the change in magnetoresistance caused by spin-dependent scattering can be attained enough in the parallel direction
Implementation Method 2
a first pinned layer of a magnetic layer, a nonmagnetic metal layer, and a second pinned layer of a magnetic layer stacked in this order with the first and second pinned layers being antiferromagnetically coupled
Implementation Method 3
enhancing bulk scattering and suppressing effective magnetization to increase magnetoresistance
Data Source
AI summary
A magnetoresistive sensor comprises stacked layers. The stacked layers comprises a first magnetic layer, a second non-magnetic intermediate layer, and a second magnetic layer in which a direction of magnetization is variable depending on an external magnetic field. The first magnetic layer, the second non-magnetic intermediate layer, and the second magnetic layer are stacked in this order to form the stacked layers. The first magnetic layer has a first ferromagnetic layer in which a direction of magnetization is pinned relative to the external magnetic field, a first non-magnetic intermediate layer, and a second ferromagnetic layer in which a direction of magnetization is pinned in a direction opposite to the direction of magnetization of the first ferromagnetic layer. The first ferromagnetic layer, the first non-magnetic intermediate layer, and the second ferromagnetic layer are stacked in this order. A sense current flows through the stacked layers substantially in the direction of stacking. A ratio of a layer thickness of the second ferromagnetic layer to a layer thickness of the first ferromagnetic layer is in a range between 1.4 and 1.9. A ratio of a product of a saturation magnetization and the layer thickness of the second ferromagnetic layer to a product of a saturation magnetization and the layer thickness of the first ferromagnetic layer is in a range between 0.9 and 1.1.