Magnetic Memory Element With Perpendicular Anisotropy Free Layer
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Solution Overview
Problem
Magnetic random access memories (MRAMs) face challenges in reducing writing current while maintaining high-speed operation and scalability, as existing methods like spin transfer magnetization switching require high currents and are prone to reliability issues and writing errors.
Innovation Solution
A magnetic memory element using domain wall motion with a ferromagnetic material having perpendicular magnetic anisotropy as the first magnetization free layer and in-plane magnetic anisotropy for the second magnetization free layer, along with a ferromagnetic reference layer, to reduce writing current and enhance reading signal strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a magnetic field is used to switch magnetization direction for high-speed writing, then writing speed is improved (1 nano-second or less), but writing current increases to a few mA
Solution Approach 1:
The patent replaces the magnetic field-based writing mechanism (which requires high current) with a spin transfer torque mechanism. A current is made to flow through the magnetic memory element itself, utilizing spin-polarized electrons to switch magnetization direction, thereby reducing writing current while maintaining high-speed operation
Solution Approach 2:
The patent introduces a spin-polarized electron current as an intermediary between the electrical current and magnetization switching. The current flows through a magnetic tunnel junction, generating spin-polarized electrons that transfer angular momentum to the free layer, enabling low-current magnetization switching
2Use of energy by moving object
If spin transfer magnetization switching is used to reduce writing current, then writing current is reduced and scaling performance is improved, but reliability decreases due to writing errors in reading operation
Solution Approach 1:
The patent segments the magnetic memory element into distinct functional regions: a magnetic tunnel junction for reading operation and a separate free layer region for writing operation. The writing current flows through the free layer while the reading current passes through the tunnel junction, physically separating the two current paths to prevent writing errors during reading
Solution Approach 2:
The patent uses the spin transfer torque effect as an intermediary mechanism that allows writing current to flow through the magnetic layers without passing through the insulating tunnel barrier. This separates the writing current path from the reading current path, eliminating the reliability issues associated with current-induced magnetization switching during read operations
3Speed
If magnetic field switching is used for data writing, then writing speed is high, but chip area increases and power consumption increases
Solution Approach 1:
The patent replaces the external magnetic field generation system (wiring lines and current sources) with a direct spin transfer torque mechanism. The writing current flows vertically through the magnetic tunnel junction and free layer, eliminating the need for peripheral wiring and reducing chip area while maintaining high-speed writing capability
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 achieves a reduced writing current, large reading signal, and compact cell size, enabling high-speed and cost-effective MRAM operation comparable to existing embedded memory technologies.
Implementation Method 1
a first magnetization free layer formed of a ferromagnetic material having perpendicular magnetic anisotropy
Implementation Method 2
a second magnetization free layer provided near the first magnetization free layer and formed of a ferromagnetic material having in-plane magnetic anisotropy, a reference layer formed of a ferromagnetic material having in-plane magnetic anisotropy
Implementation Method 3
A magnetic memory element using domain wall motion with a ferromagnetic material having perpendicular magnetic anisotropy as the first magnetization free layer
Implementation Method 4
A magnetic memory element using domain wall motion... enabling high-speed and cost-effective MRAM operation
Data Source
AI summary
A magnetic memory element includes: a first magnetization free layer formed of a ferromagnetic material having perpendicular magnetic anisotropy; a second magnetization free layer provided near the first magnetization free layer and formed of a ferromagnetic material having in-plane magnetic anisotropy; a reference layer formed of a ferromagnetic material having in-plane magnetic anisotropy; and a non-magnetic layer provided between the second magnetization free layer and the reference layer. The first magnetization free layer includes: a first magnetization fixed region of which magnetization is fixed, a second magnetization fixed region of which magnetization is fixed, and a magnetization free region which is connected to the first magnetization fixed region and the second magnetization fixed region, and of which magnetization can be switched. The second magnetization free layer is included in the first magnetization free layer in a plane parallel to a substrate. The second magnetization free layer is provided in a first direction away from the magnetization free region in the plane.