MRAM Stacked Structure with Segmented Magnetic Layer
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Solution Overview
Problem
In magnetic random access memory (MRAM) devices, reducing the reversal current for fast magnetization reversal is essential to improve performance, but existing configurations face challenges in achieving this while maintaining thermal stability and bit density.
Innovation Solution
A nonvolatile memory device with a stacked structure comprising a first magnetic layer, a second magnetic layer with distinct portions, and a nonmagnetic layer, where the second magnetic layer's magnetic resonance frequency is lower than the first, allowing for reduced programming current and enhanced thermal stability through ferromagnetic or antiferromagnetic coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a magnetic tunnel junction (MTJ) element is used for data memory unit, then fast and high-capacity memory performance is achieved, but the reversal current remains too high for fast magnetization reversal
Solution Approach 1:
The second magnetic layer is divided into a first portion and a second portion with different magnetic resonance frequencies. This segmentation allows selective resonance excitation of the first portion at lower current, enabling faster magnetization reversal without requiring high current across the entire layer.
Solution Approach 2:
The patent utilizes magnetic resonance frequency excitation to induce oscillatory magnetization in the first portion of the second magnetic layer. By applying current at the resonant frequency, the magnetization reversal is amplified and accelerated, reducing the required reversal current and improving switching speed.
2Use of energy by moving object
If the magnetic resonance frequency of the second magnetic layer is reduced to enable lower programming current, then thermal stability may be compromised
Solution Approach 1:
Different portions of the second magnetic layer are assigned different magnetic resonance frequencies through compositional or structural variations. The first portion is designed with lower resonance frequency for efficient current-driven switching, while the second portion maintains higher frequency characteristics that contribute to thermal stability, allowing both requirements to be satisfied locally.
Solution Approach 2:
The second magnetic layer is constructed as a composite of two portions with different magnetic properties. This composite structure enables the system to exhibit both low-frequency resonance characteristics (for low programming current) and high thermal stability (maintained by the second portion), resolving the contradiction between energy efficiency and stability.
3Quantity of substance
If bit density is increased to improve memory capacity, then the available area per bit decreases, making it harder to maintain thermal stability and reduce programming current
Solution Approach 1:
The patent utilizes the frequency dimension by creating multiple magnetic resonance frequency modes within the second magnetic layer. This additional degree of freedom allows the system to achieve high bit density while maintaining thermal stability through frequency-selective excitation, as the different frequency portions can be independently optimized for their respective functions.
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 solution effectively reduces the programming current and enhances thermal stability, enabling faster programming operations and improved memory retention, while maintaining high bit density and thermal stability factors.
Implementation Method 1
enhanced thermal stability through ferromagnetic or antiferromagnetic coupling
Implementation Method 2
enhanced thermal stability through ferromagnetic or antiferromagnetic coupling
Implementation Method 3
A magnetic resonance frequency of the first portion is different from a magnetic resonance frequency of the second portion
Data Source
AI summary
According to one embodiment, a memory device includes a stacked structure and a controller. The stacked structure includes a first magnetic layer, a second magnetic layer stacked with the first magnetic layer, and a first nonmagnetic layer provided between the first magnetic layer and the second magnetic layer. The second magnetic layer includes a first portion and a second portion stacked with the first portion. A magnetic resonance frequency of the first portion is different from a magnetic resonance frequency of the second portion. The controller is electrically connected to the stacked structure and causes a pulse current to flow in the stacked body in a first period. A length of the first period is not less than 0.9 times and not more than 1.1 times the absolute value of an odd number times of the reciprocal of a magnetic resonance frequency of the second magnetic layer.