Spin-Transfer MRAM Memory Layer Structure
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Solution Overview
Problem
Existing memory devices face challenges in achieving a high magnetoresistance change ratio, suppressing spin injection current, and increasing breakdown voltage, making it difficult to maintain a balance of properties for reliable and efficient information storage.
Innovation Solution
A memory device configuration with a memory layer sandwiched by insulating intermediate layers and fixed magnetic layers, where at least one intermediate layer is accompanied by a nonmagnetic conductive layer, allows for spin-polarized electron injection to reverse the magnetization direction, enhancing spin injection efficiency and maintaining a high magnetoresistance change ratio while increasing breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current is passed through addressing wires to reverse magnetization in an ordinary MRAM, then information can be stored, but the current value needed increases as element size decreases
Solution Approach 1:
The patent replaces the conventional current magnetic field method (electromagnetic mechanism) with spin injection mechanism. By passing current vertically through the magnetic memory device, spin-polarized electrons are injected into the memory layer to induce magnetization reversal, eliminating the need for high current through addressing wires and enabling lower power consumption in scaled devices
Solution Approach 2:
The patent changes the current flow direction from horizontal (through addressing wires) to vertical (through the stacked magnetic layers). This dimensional change allows direct spin injection into the memory layer, achieving magnetization reversal with lower current and enabling better scaling to smaller elements
2Use of energy by moving object
If magnetization reversal is achieved by spin injection, then lower current is required, but it becomes difficult to simultaneously ensure high magnetoresistance change ratio and suppress spin injection current
Solution Approach 1:
The patent segments the magnetic memory device into distinct functional layers: fixed magnetic layer, memory layer, and cap layer, separated by intermediate layers. This segmentation allows independent optimization of each layer's properties - the fixed layer provides stable reference magnetization, the memory layer enables low-current spin injection reversal, and the cap layer protects the structure - thereby achieving both low operating current and high magnetoresistance change ratio
Solution Approach 2:
The patent introduces intermediate layers between the magnetic layers, which act as mediators to control spin transport and tunneling. These intermediate layers enable efficient spin injection at low current while maintaining high magnetoresistance change ratio through controlled electron transport, resolving the contradiction between low power consumption and high reliability
3Loss of information
If the magnetization direction is reversed by current magnetic field, then information storage is achieved, but the device complexity increases with separate addressing wires
Solution Approach 1:
The patent merges the read and write functions into a single vertical current path through the stacked magnetic layers. The same current that flows through the device for reading also provides spin injection for writing, eliminating the need for separate addressing wires and reducing device complexity while maintaining full information storage capability
Solution Approach 2:
The vertical current path serves multiple functions simultaneously: it provides readout current for detecting magnetization state and spin injection current for writing information. This multi-functionality reduces the number of required components and simplifies the overall device structure compared to conventional MRAM with separate addressing wires
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 ensures a high magnetoresistance change ratio, reduces the current required for magnetization reversal, and increases the breakdown voltage, resulting in a memory device with excellent balance of properties and reduced power consumption for stable and reliable information storage.
Implementation Method 1
spin-polarized electrons are injected thereinto in the stacking direction to change the magnetization direction of the memory layer
Implementation Method 2
a memory layer which uses the magnetization state of a ferromagnetic layer to store information
Data Source
AI summary
A memory device includes: a memory layer that retains information based on a magnetization state of a magnetic material, a first intermediate layer and a second intermediate layer that are provided to sandwich the memory layer and are each formed of an insulator, a first fixed magnetic layer disposed on an opposite side of the first intermediate layer from the memory layer, a second fixed magnetic layer disposed on an opposite side of the second intermediate layer from the memory layer, and a nonmagnetic conductive layer provided between either the first intermediate layer or the second intermediate layer and the memory layer, the memory device being configured so that spin-polarized electrons are injected thereinto in a stacking direction to change the magnetization direction of the memory layer, thereby storing information in the memory layer.