Magnetoresistance Element with Perpendicular and Parallel Layers
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Solution Overview
Problem
Conventional magnetic random access memory (MRAM) technologies face challenges in minimizing the current required for writing, achieving high-speed writing, and maximizing memory capacity, particularly as memory cells become smaller, due to limitations in the spin torque write technique.
Innovation Solution
A magnetoresistance effect element is designed with a first ferromagnetic layer having invariable magnetization perpendicular to the film plane, a second ferromagnetic layer with variable magnetization, a nonmagnetic layer in between, and a third ferromagnetic layer with variable magnetization parallel to the film plane, where spin-polarized electrons induce precession movement and a microwave magnetic field is applied to facilitate magnetization reversal with reduced current density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the spin torque write technique is used to reverse magnetization by applying current directly to each MTJ element, then the current amount required for writing decreases as memory cells become smaller, but the write current density remains too high (around 3 MA/cm2) to achieve large-capacity memory
Solution Approach 1:
The patent segments the write current path from the read current path by introducing a dedicated write wire that applies magnetic field for writing, while the MTJ element uses a separate path for reading. This segmentation allows optimization of each path independently, enabling low-current writing through magnetic field while maintaining small cell size for high capacity.
Solution Approach 2:
The patent changes the writing mechanism from direct spin torque (high current density) to magnetic field writing through a write wire (low current density). By changing the physical parameter of the writing method from electrical current through MTJ to magnetic field from write wire, the write current density is reduced to below 1 MA/cm2, enabling large-capacity memory.
2Quantity of substance
If memory cells are made smaller to increase cell occupancy and memory capacity, then the current amount required for writing increases when using the current field write technique
Solution Approach 1:
The patent separates the writing function from the MTJ element structure by introducing an external write wire that generates magnetic field for writing. This segmentation allows the MTJ element to be miniaturized for high density while the write wire provides the necessary magnetic field without being constrained by cell size, thus maintaining low write current regardless of cell dimensions.
Solution Approach 2:
The patent introduces a write wire as an intermediary component that mediates the writing process. Instead of directly passing high current through the small MTJ element, the write wire acts as an intermediary that generates magnetic field to reverse magnetization, enabling small cell size with low write current.
3Ease of operation
If the magnetization of the recording layer is reversed with a magnetic field generated by applying current to the write wire (current field write technique), then writing can be performed, but the current amount required for writing becomes greater as the memory cells become smaller
Solution Approach 1:
The patent optimizes the magnetic field generation efficiency by adjusting the write wire geometry, current density distribution, and magnetic coupling between write wire and recording layer. This parameter optimization enables effective magnetization reversal with lower current amounts, maintaining writing capability while reducing energy consumption.
Solution Approach 2:
The patent enhances the magnetic field strength locally at the MTJ element position by optimizing the write wire structure and positioning. This local quality enhancement ensures effective writing at each cell location while minimizing overall current requirements, maintaining writing capability with reduced energy 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
This configuration significantly reduces the current required for writing, enables high-speed writing, and allows for the creation of smaller-sized magnetoresistance effect elements, thereby enhancing memory capacity and performance.
Implementation Method 1
spin-polarized electrons being injected into the second ferromagnetic layer by flowing a current in the direction perpendicular to the film planes between the first ferromagnetic layer and the third ferromagnetic layer
Implementation Method 2
precession movement being induced in the magnetization of the third ferromagnetic layer by injecting the spin-polarized electrons into the third ferromagnetic layer from the second ferromagnetic layer through the second nonmagnetic layer
Implementation Method 3
a microwave magnetic field of a frequency corresponding to the precession movement being applied to the second ferromagnetic layer
Implementation Method 4
magnetic random access memories (MRAM) including magnetoresistance effect elements each exhibiting the giant magnetoresistive (GMR) effect
Implementation Method 5
magnetic random access memories using ferromagnetic tunnel junctions each exhibiting the tunnel magnetoresistive (TMR) effect
Data Source
AI summary
A magnetoresistance effect element includes: a first ferromagnetic layer having invariable magnetization perpendicular to a film plane; a second ferromagnetic layer having variable magnetization perpendicular to the film plane; a first nonmagnetic layer interposed between the first ferromagnetic layer and the second ferromagnetic layer; a third ferromagnetic layer provided on an opposite side of the second ferromagnetic layer from the first nonmagnetic layer, and having variable magnetization parallel to the film plane; and a second nonmagnetic layer interposed between the second and third ferromagnetic layers. Spin-polarized electrons are injected into the second ferromagnetic layer by flowing a current in the direction perpendicular to the film planes between the first and third ferromagnetic layers, precession movement is induced in the magnetization of the third ferromagnetic layer by injecting the spin-polarized electrons, and a microwave magnetic field of a frequency corresponding to the precession movement is applied to the second ferromagnetic layer.