ST-RAM Magnetic Element Reflective Surface Reduces Switching Current
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current spin transfer-based current perpendicular to plane (CPP) magnetic elements face challenges in achieving efficient spin torque transfer due to the thin free magnetic layer, which limits dense packing and increases switching current requirements.
Innovation Solution
Incorporating an electronically reflective surface and/or a permanent magnet layer with perpendicular anisotropy to enhance spin torque transfer efficiency by increasing the effective thickness of the free magnetic layer and reducing switching current needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the free magnetic layer is made thicker to allow efficient spin torque transfer, then spin torque transfer efficiency is improved, but switching current requirement increases and fringe magnetic field interference increases
Solution Approach 1:
The patent introduces an electronically reflective surface at the bottom of the free magnetic layer, creating a virtual image of the layer that effectively doubles its magnetic influence without increasing physical thickness. This dimensional approach (adding a reflective interface) allows the thin physical layer to produce effects equivalent to a thicker layer, resolving the contradiction between maintaining thin geometry and achieving sufficient spin torque transfer efficiency
Solution Approach 2:
The electronically reflective surface acts as an intermediary that mediates between the thin free magnetic layer and the spin-polarized current. By introducing this intermediate reflective interface, the system achieves enhanced spin torque transfer efficiency without requiring increased layer thickness, thus avoiding the penalty of higher switching current requirements
2Reliability
If the free magnetic layer is made thicker to allow efficient spin torque transfer, then spin torque transfer efficiency is improved, but fringe magnetic field interference with neighboring elements increases
Solution Approach 1:
By adding the electronically reflective surface dimension, the patent creates a virtual extension of the magnetic layer that enhances its magnetic field influence for spin torque transfer without increasing the physical footprint. This allows efficient coupling with the reference layer while confining the physical source of fringe fields to the original thin layer dimensions, reducing interference with neighboring elements
Solution Approach 2:
The reflective surface is localized specifically at the bottom interface of the free magnetic layer, creating enhanced magnetic interaction only where needed for spin torque transfer. This localized enhancement improves efficiency without requiring uniform thickening of the layer throughout, thereby minimizing fringe field generation in regions away from the intended interaction zone
3Use of energy by moving object
If the free magnetic layer is made thinner to reduce switching current, then switching current requirement is reduced, but spin torque transfer efficiency decreases
Solution Approach 1:
The patent compensates for the reduced physical thickness by introducing the electronically reflective surface, which creates a virtual image that extends the effective magnetic interaction distance. This allows the physical layer to remain thin (reducing switching current) while the effective magnetic influence is enhanced (maintaining spin torque transfer efficiency) through the additional dimensional element of the reflective interface
4Productivity
If elements are packed more densely to increase storage capacity, then packing density is improved, but fringe magnetic field interference from each element increases
Solution Approach 1:
By confining the free magnetic layer to thin dimensions while using the reflective surface to enhance magnetic interaction, the patent reduces the lateral spread of fringe fields. This allows elements to be packed more densely because each element's magnetic influence is more confined vertically, reducing cross-talk with neighboring elements and enabling higher packing density
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 allows for more efficient magnetization switching with reduced switching current and improved packing density in memory devices by effectively increasing the spin diffusion length and minimizing fringe magnetic fields.
Implementation Method 1
spin transfer can be used as an alternative to, or in addition to, an external magnetic field in switching current perpendicular to plane (CPP) configurations of magnetic elements
Implementation Method 2
The free magnetic layer may be provided with an electronically reflective surface that reflects a portion of the spin polarized current incident thereon back into the free magnetic layer
Implementation Method 3
a CPP magnetic element includes a permanent magnet layer, which has perpendicular anisotropy, in order to bias a free magnetic layer of the magnetic element
Implementation Method 4
a permanent magnet layer with perpendicular anisotropy to enhance spin torque transfer efficiency
Data Source
AI summary
In order to increase an efficiency of spin transfer and thereby reduce the required switching current, a current perpendicular to plane (CPP) magnetic element for a memory device includes either one or both of a free magnetic layer, which has an electronically reflective surface, and a permanent magnet layer, which has perpendicular anisotropy to bias the free magnetic layer.