Magnetoresistive Element With Segmented Reference Layers
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Solution Overview
Problem
Magnetic random access memory (MRAM) faces challenges in reducing power consumption and increasing capacity due to its recording principle, which involves magnetization inversion using a current magnetic field, and existing techniques for enhancing spin torque resistance in reference layers are insufficient, particularly in terms of external magnetic field resistance.
Innovation Solution
A magnetoresistive element with a laminated structure comprising multiple fixed layers, an intermediate non-magnetic layer, and a recording layer, where the first fixed layer has a larger area than the second fixed layer, providing high external magnetic field and spin torque resistance, thereby stabilizing data storage operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the area of the reference layer is increased to achieve high spin torque resistance, then spin torque resistance is improved, but external magnetic field resistance deteriorates
Solution Approach 1:
The reference layer is divided into multiple sub-layers (first reference layer, second reference layer, third reference layer) with different functions. The first reference layer provides spin torque resistance, while the second and third reference layers provide external magnetic field resistance through SAF structure, allowing both requirements to be met simultaneously without increasing overall area
Solution Approach 2:
The reference layer uses a composite structure combining ferromagnetic layers (CoFeB, CoFe) with non-magnetic spacer layers (Ru, Ta) to create SAF structure. This composite approach enables the reference layer to exhibit both high spin torque resistance and high external magnetic field resistance properties that single materials cannot provide
2Device complexity
If a single-layered reference layer configuration is used, then device structure is simple, but external magnetic field resistance is insufficient
Solution Approach 1:
The reference layer is segmented into multiple functional sub-layers where the first reference layer (CoFeB/Ru/CoFe) provides spin torque resistance and the second reference layer (CoFe/Ta/CoFe) provides external magnetic field resistance through SAF structure, achieving both requirements without excessive complexity
Solution Approach 2:
Non-magnetic spacer layers (Ru, Ta) are introduced as intermediaries between ferromagnetic layers to create SAF structure. These intermediary layers enable magnetic coupling while maintaining structural simplicity and providing the necessary external magnetic field resistance
3Reliability
If the area of the reference layer is increased relative to the recording layer, then spin torque resistance is improved, but the device area and power consumption increase
Solution Approach 1:
The reference layer is segmented into multiple sub-layers with different areas and functions. The first reference layer has larger area for spin torque resistance, while subsequent layers have smaller areas, reducing overall device area and power consumption compared to uniformly large reference layers
Solution Approach 2:
Different regions of the reference layer structure have different qualities: the first reference layer region provides spin torque resistance, while the second reference layer region provides external magnetic field resistance. This local differentiation allows optimized performance without increasing overall device power consumption
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 proposed structure enhances the external magnetic field resistance and spin torque resistance, allowing for stable data storage and reduced power consumption, enabling efficient operation and increased capacity in MRAM devices.
Implementation Method 1
a spin-polarized electron that has passed through a magnetic material is injected into a different magnetic material and thus, magnetization inversion is caused in the different magnetic material
Implementation Method 2
The magnetic random access memory (MRAM) performs the data storage using a magnetization direction of a magnetic material
Data Source
AI summary
A magnetoresistive element includes a laminated structure including a plurality of fixed layers, an intermediate layer formed of a non-magnetic material, and a recording layer, the plurality of fixed layers being laminated via a non-magnetic layer, the plurality of fixed layers having at least a first fixed layer and a second fixed layer, the following formula being satisfied: S1>S2 (wherein S1 is an area of a portion of the first fixed layer adjacent to the intermediate layer, which faces the intermediate layer, and S2 is an area of the fixed layer having the smallest area out of the fixed layers other than the first fixed layer).