Scalable Magnetoresistive Element Thermal Stability
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Solution Overview
Problem
Current magnetic random access memory (MRAM) technologies face challenges in achieving sufficient thermal stability and scalable non-volatile storage due to limitations in materials with perpendicular magnetic anisotropy, which affect the coherence of spin-polarized switching currents and tunneling magnetoresistance, especially at higher temperatures and smaller device sizes.
Innovation Solution
A magnetoresistive element with a free ferromagnetic layer, a pinned ferromagnetic layer, and a nonmagnetic tunnel barrier layer, comprising specific elements like Fe, Co, Ni, V, Cr, Mo, B, P, and Si, forming a coherent body-centered cubic structure, and additional nonmagnetic metal layers to enhance perpendicular magnetic anisotropy and reduce switching current density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If magnetic materials with perpendicular anisotropy are used to achieve thermal stability, then thermal stability is improved, but damping constant increases and spin polarization decreases
Solution Approach 1:
The patent employs composite magnetic layer structures combining CoFeB with other materials to achieve both perpendicular magnetic anisotropy for thermal stability and low damping constant for reliable spin-polarized current switching. The composite structure allows optimization of both competing properties through material composition and interface engineering.
Solution Approach 2:
The patent modifies material parameters including composition ratios, layer thicknesses, and crystalline structure to simultaneously achieve high thermal stability and low damping constant. By controlling the perpendicular magnetic anisotropy energy and adjusting layer dimensions, the patent optimizes both thermal stability and spin transport properties.
2Quantity of substance
If device size is reduced to increase storage density, then storage capacity is improved, but thermal stability deteriorates
Solution Approach 1:
The patent introduces perpendicular magnetic anisotropy to change the magnetic energy landscape, allowing thermal stability to be maintained at smaller device dimensions. By switching from in-plane to perpendicular magnetization, the patent achieves scaling while preserving stability through enhanced anisotropy energy barriers.
Solution Approach 2:
The patent creates localized perpendicular magnetic anisotropy at specific interfaces within the magnetic tunnel junction structure. By engineering the interface properties between magnetic layers and adjacent materials, the patent achieves local enhancement of magnetic anisotropy that maintains thermal stability even as overall device size decreases.
3Use of energy by moving object
If spin-polarized switching current density is reduced to lower power consumption, then energy efficiency is improved, but magnetization reversal becomes difficult
Solution Approach 1:
The patent modifies the magnetic layer composition and structure to reduce saturation magnetization and damping constant, thereby lowering the critical switching current density while maintaining reliable magnetization reversal. By optimizing the CoFeB layer parameters and interface properties, the patent achieves low-power switching without sacrificing reversal efficiency.
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 provides improved thermal stability, high tunneling magnetoresistance, and low spin-polarized switching current density, enabling efficient data storage and retrieval in MRAM devices, particularly at smaller sizes and higher temperatures.
Implementation Method 1
Low density of the spin-polarized switching current (JS≤1·106 A/cm2) and high tunneling magnetoresistance (TMR≥150%) originate from a coherent spin-dependent tunneling of highly spin-polarized electrons
Implementation Method 2
The spin-polarized current can reverse the magnetization direction of the free layer
Implementation Method 3
The MTJ comprising magnetic layers made of materials having a perpendicular anisotropy (or perpendicular direction of magnetization in an equilibrium state) can provide a substantial thermal stability (Δ≥60)
Data Source
AI summary
One embodiment of a magnetoresistive element comprises: a free ferromagnetic layer comprising a reversible magnetization direction directed substantially perpendicular to a film surface in its equilibrium state; a pinned ferromagnetic layer comprising a fixed magnetization direction directed substantially perpendicular to the film surface; a nonmagnetic tunnel barrier layer disposed between the free ferromagnetic layer and the pinned ferromagnetic layer and having a direct contact with the free and pinned ferromagnetic layers; a first nonmagnetic conductive layer disposed adjacent to and having a direct contact with a side of a free ferromagnetic layer opposite to the tunnel barrier layer; and a second nonmagnetic conductive layer disposed adjacent to a side of the pinned ferromagnetic layer opposite to the tunnel barrier layer, wherein the free ferromagnetic layer and the pinned ferromagnetic layers comprise at least one element selected from the group consisting of Fe, Co, and Ni, at least one element selected from the group consisting from V, Cr, and Mo, and at least one element selected from the group consisting of B, P, C, and Si, and wherein the first nonmagnetic conductive layer comprises an oxide. Other embodiments are described as shown.