Magnetoresistive Element Alloy Composition for Low Current MRAM
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Solution Overview
Problem
The spin transfer torque writing method for magnetoresistive random access memory (MRAM) requires a higher electric current for magnetization reversal than what can be generated by selection transistors, making it difficult to achieve small cell sizes and low writing currents simultaneously, while also compromising thermal stability for data retention.
Innovation Solution
A magnetoresistive effect element with a free layer made of alloys containing elements like Fe, Co, Ni, Ru, Rh, Pd, Ag, Re, Os, Ir, Pt, and Au, and Mn, with a nonmagnetic spacer layer, allows for bidirectional electric current to vary the magnetization direction, reducing the saturation magnetization and crystal magnetic anisotropic energy to decrease the reversing current while maintaining thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the spin transfer torque writing method is used to decrease the writing electric current, then the magnetization reversal current decreases, but the thermal stability for data retention deteriorates
Solution Approach 1:
The patent applies parameter changes by modifying the material composition of the magnetization variable layer, specifically using alloys containing elements like Fe, Co, Ni combined with Ru, Rh, Pd, Ag, Re, Os, Ir, Pt, Au and Mn. This changes the magnetic parameters (saturation magnetization and crystal magnetic anisotropic energy) to achieve lower reversal current while maintaining thermal stability through controlled material properties
Solution Approach 2:
The patent uses composite materials by creating a magnetization variable layer with multi-element alloys combining transition metals (Fe, Co, Ni) with noble metals (Ru, Rh, Pd, Ag, Re, Os, Ir, Pt, Au) and Mn. This composite structure enables simultaneous optimization of magnetic reversal properties and thermal stability that cannot be achieved with single-element materials
2Area of moving object
If the size of the TMR element is decreased for high-density MRAMs, then the cell size decreases, but the coercive force increases making writing current larger
Solution Approach 1:
The patent changes the magnetic parameters of the magnetization variable layer by using specific multi-element alloys that maintain low coercive force even at reduced cell sizes. The alloy composition is optimized to preserve magnetic softness properties that enable low-current writing in scaled-down devices
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 enables magnetization reversal with a low electric current and high thermal stability, allowing for scalable and efficient MRAM operation.
Implementation Method 1
A bidirectional electric current flowing through the first magnetic layer, the first spacer layer, and the second magnetic layer makes the magnetization direction of the second magnetic layer variable
Implementation Method 2
a magnetoresistive effect element (TMR element) that achieves the tunneling magnetoresistive effect as a memory cell
Data Source
AI summary
A magnetoresistive effect element includes a first magnetic layer, a second magnetic layer, and a first spacer layer. The first magnetic layer has an invariable magnetization direction. The second magnetic layer has a variable magnetization direction, and contains at least one element selected from Fe, Co, and Ni, at least one element selected from Ru, Rh, Pd, Ag, Re, Os, Ir, Pt, and Au, and at least one element selected from V, Cr, and Mn. The spacer layer is formed between the first magnetic layer and the second magnetic layer, and made of a nonmagnetic material. A bidirectional electric current flowing through the first magnetic layer, the spacer layer, and the second magnetic layer makes the magnetization direction of the second magnetic layer variable.