Magnetoresistive Element with Antiferromagnetic Free Layer
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Solution Overview
Problem
Magnetoresistive effect elements used in magnetic memories face challenges with high power consumption and current density, leading to element destruction and interaction with adjacent cells, especially when using the spin injection method, which requires low current writing and high reliability without heat fluctuation.
Innovation Solution
A magnetoresistive effect element with a magnetization free layer subjected to antiferromagnetic coupling, featuring a tunnel barrier layer and pinned layers with specific materials like Ru, Rh, and Cu, allowing for low power consumption and reduced current writing while maintaining reliability and minimizing interaction with adjacent cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the spin injection method is used for writing, then low current writing is achieved, but element destruction occurs due to high power consumption and current density
Solution Approach 1:
The patent changes the writing mechanism from spin injection (current-based) to magnetic field-based writing using a write head. This parameter change in the writing method eliminates the high current density requirement while achieving reliable magnetization inversion in the storage layer, thus preventing element destruction.
Solution Approach 2:
The patent introduces a write head as an intermediary component that generates the magnetic field needed for writing. Instead of directly applying current to the memory element, the write head mediates the writing process by converting electrical current into a magnetic field that acts on the storage layer, thereby avoiding element destruction.
2Power
If high voltage is applied to increase output voltage, then desired output voltage is obtained, but magnetoresistance change rate decreases
Solution Approach 1:
The patent uses a pinned layer with perpendicular magnetization instead of in-plane magnetization. This parameter change in the magnetization orientation enables the TMR element to maintain high magnetoresistance change rate even when operated at higher voltages, thus resolving the trade-off between output voltage and magnetoresistance change rate.
3Productivity
If magnetic material films are used for writing, then writing efficiency is improved, but interaction with adjacent cells occurs
Solution Approach 1:
The patent employs a write head with localized magnetic pole structures that concentrate the magnetic field precisely at the target memory cell location. This local quality enhancement ensures that the magnetic field affects only the intended cell and not adjacent cells, eliminating harmful interactions while maintaining writing efficiency.
4Speed
If current density is increased to improve writing speed, then writing time is reduced, but power consumption increases
Solution Approach 1:
The patent replaces the electrical current-based writing mechanism with a magnetic field-based mechanism using a write head. This substitution allows writing to occur through magnetic field induction rather than direct current flow, achieving fast writing speeds through efficient magnetic field generation while significantly reducing power consumption compared to high current density methods.
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 enables reliable, low-power magnetic memory operation with reduced current requirements and improved thermal agitation resistance, preventing element destruction and false operations due to heat fluctuations.
Implementation Method 1
a magnetoresistive effect element which has a sandwich structure film formed by inserting a single layer of a dielectric between two ferromagnetic layers, which causes a current to flow perpendicularly to the surface, and utilizes a tunnel current, the so-called 'ferromagnetic TMR (Tunneling Magneto-Resistance effect) element'
Implementation Method 2
A ferromagnetic single tunnel junction having a structure obtained by providing one of the ferromagnetic layers having the tunnel barrier layer of a ferromagnetic single tunnel junction between with an antiferromagnetic layer
Implementation Method 3
a write method using a spin injection method is proposed (see, for example, U.S. Pat. No. 6,256,223). This spin injection method utilizes inversion of the magnetization direction of the magnetic recording layer obtained by injecting a spin-polarized current into the magnetic recording layer of the memory element
Data Source
AI summary
It is made possible to provide a highly reliable magnetoresistive effect element and magnetic memory that operate with low power consumption and low current writing. The magnetoresistive effect element includes: a magnetization free layer including at least two magnetic layers subject to antiferromagnetic coupling and a non-magnetic layer provided between the magnetic layers; a tunnel barrier layer provided on one surface of the magnetization free layer; a first magnetization pinned layer provided on an opposite surface of the tunnel barrier layer from the magnetization free layer; a non-magnetic metal layer provided on an opposite surface of the magnetization free layer from the tunnel barrier layer; and a second magnetization pinned layer provided on an opposite surface of the non-magnetic metal layer from the magnetization free layer. The first and second magnetization pinned layers are substantially the same in magnetization direction. The non-magnetic metal layer includes Cu, Ag, Au, or an alloy of them. The non-magnetic layer in the magnetization free layer includes Ru, Rh, Ir or an alloy of them.