Perpendicular Magnetic Tunnel Junction Free Layer Segmentation
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Solution Overview
Problem
Current magnetic memory devices face challenges in achieving a high MR ratio and reducing switching current for efficient data storage, which are crucial for next-generation memory devices with fast operating speed and low power consumption.
Innovation Solution
The magnetic memory device is designed with a free magnetic structure comprising two free layers of different thicknesses and a perpendicular magnetization enhancement layer, configured to achieve interface perpendicular anisotropy, allowing for increased MR ratio and reduced switching current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a magnetic tunnel junction is designed with conventional single free layer structure, then the device structure is simple, but the MR ratio is insufficient and switching current is high
Solution Approach 1:
The free layer is divided into two separate free layers (first free layer and second free layer) with different thicknesses, where each layer contributes differently to the overall magnetic properties. The first free layer has thickness greater than maximum anisotropy thickness while the second has thickness less than maximum anisotropy thickness, creating complementary effects that enhance MR ratio while managing switching current
Solution Approach 2:
Different regions of the free magnetic structure are given different local properties through varying layer thicknesses. The first free layer is designed with thickness > maximum anisotropy thickness to provide stable perpendicular magnetization, while the second free layer with thickness < maximum anisotropy thickness provides enhanced spin torque efficiency, creating local optimization throughout the structure
2Reliability
If the free layer thickness is increased to enhance perpendicular anisotropy, then the MR ratio improves, but the switching current increases
Solution Approach 1:
The free layer is segmented into two parts with different thickness characteristics. The first free layer (thickness > maximum anisotropy thickness) provides strong perpendicular anisotropy for high MR ratio, while the second free layer (thickness < maximum anisotropy thickness) has lower anisotropy energy that reduces the switching current requirement, achieving a balance between MR ratio and switching current
Solution Approach 2:
The thickness parameter of the free layer is changed from a single value to a distributed range by creating two distinct layers. By controlling the thickness of each layer relative to the maximum anisotropy thickness, the patent optimizes the competition between perpendicular anisotropy energy (favoring thicker layers for higher MR) and switching current (favoring thinner layers for lower energy), achieving simultaneous improvement in both parameters
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 MR ratio while minimizing the switching current, making the magnetic memory device more efficient for high-density and high-speed applications.
Implementation Method 1
the first and second free layers may be configured to have an interface perpendicular anisotropy
Implementation Method 2
The magnetic tunnel junction may include two magnetic layers and a tunnel barrier layer interposed therebetween. Resistance of the magnetic tunnel junction may vary depending on magnetization orientations of the magnetic layers
Data Source
AI summary
A magnetic memory device may include a free magnetic structure and a reference magnetic structure that are separated from each other by a tunnel barrier. The free magnetic structure may include an exchange-coupling layer, and first and second free layers that are separated from each other by the exchange-coupling layer. The first free layer may be provided between the second free layer and the tunnel barrier. A thickness of the first free layer may be greater than a first maximum anisotropy thickness, being the thickness at which the first free layer has maximum perpendicular anisotropy. A thickness of the second free layer may be smaller than a second maximum anisotropy thickness, being the thickness at which the second free layer has maximum perpendicular anisotropy. A magnetic tunnel junction having two free layers with different thicknesses can enable a magnetic memory device that has increased MR ratio and reduced switching current.