Stray Field Applying Layers for SOT MRAM Power Reduction
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Solution Overview
Problem
Magnetic random access memory (MRAM) devices require an external magnetic field for operation, which increases power consumption and overall device resistance when attempting to replace it with stacked magnetic functional layers.
Innovation Solution
The magnetic memory device incorporates multiple perpendicular spin-orbit torque elements and stray field applying layers, where the stray field applying layers are disposed between the perpendicular spin-orbit torque elements to generate a magnetic field that flips the free layer during Spin-Orbit-Torque (SOT) operations without an external magnetic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an external magnetic field is used for SOT operation, then the magnetic moment can be flipped in the ferromagnetic material, but additional devices and power consumption are required
Solution Approach 1:
The patent extracts the external magnetic field requirement from the SOT operation by introducing a stray field applying layer that generates the necessary magnetic field internally. This removes the need for external magnetic field devices while maintaining the magnetic moment flip capability.
Solution Approach 2:
The stray field applying layer acts as an intermediary component that generates the magnetic field needed for SOT operation. This intermediary structure enables the magnetic moment flip without requiring external magnetic field devices, thus reducing power consumption.
2Ease of operation
If stacked magnetic functional layers are used to replace external magnetic field, then the external magnetic field requirement is eliminated, but the overall resistance increases leading to higher operating current
Solution Approach 1:
The patent applies local quality by positioning the stray field applying layer specifically at the interface between the heavy metal layer and ferromagnetic material, rather than stacking magnetic functional layers throughout the entire structure. This localized approach generates the necessary magnetic field only where needed, avoiding the resistance increase that would result from stacking magnetic layers throughout the current path.
3Ease of operation
If stray field applying layers are disposed between perpendicular spin-orbit torque elements, then SOT flip can be performed without external magnetic field, but the structure becomes more complex
Solution Approach 1:
The patent merges the stray field applying layer with the existing heavy metal layer and ferromagnetic material structure. Instead of adding completely separate components, the stray field applying layer is integrated into the interface structure, combining multiple functions (current conduction, magnetic field generation, and SOT operation) into a unified structure that reduces overall device complexity.
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 reduces the operating current of the device and lowers power consumption while maintaining the high performance of magnetic memory devices, without increasing the resistance of the read current.
Implementation Method 1
The mechanism of magnetic tunnel junction device to read/write by Spin-Orbit-Torque (SOT) is that a current flowing into a heavy metal layer generates SOT at the interface, and the resultant moment of the external magnetic field H will flip the magnetic moment perpendicular to film surface in the ferromagnetic material at the interface
Implementation Method 2
The stray field applying layers are disposed between the perpendicular spin-orbit torque elements, and each of the stray field applying layers extends horizontally between the first electrode and the second electrode
Data Source
AI summary
A magnetic memory device includes multiple perpendicular spin-orbit torque (SOT) elements and multiple stray field applying layers. Each of the perpendicular SOT elements at least includes a first electrode, a second electrode, and a magnetic tunnel junction (MTJ). The MTJ is disposed on the first electrode, and the second electrode is disposed on the MTJ. The stray field applying layers are disposed between the perpendicular SOT elements, and each of the stray field applying layers extends horizontally between the first electrode and the second electrode. These layers generate the magnetic field required to flip the free layer during SOT, eliminating the need for an additional magnetic field during reading and writing. Additionally, the stray field applying layer horizontally disposed on two sides of the MTJ doesn't increase device height, allowing reduction of write current without increasing the read current resistance, thus reducing the power consumption.