BCC Iron Cobalt Multilayers for MRAM PMA
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Solution Overview
Problem
Spin torque magnetic random access memory (MRAM) faces challenges in achieving high tunnel magnetoresistance (MR) with magnesium oxide (MgO) tunnel barriers, requiring a material with a two-dimensional interface and sufficient lattice match, while also exhibiting perpendicular magnetic anisotropy (PMA), which is difficult to develop simultaneously with high MR and large PMA.
Innovation Solution
A multilayer magnetic material comprising alternating body-centered cubic (BCC) iron and BCC or amorphous cobalt layers, with each layer thickness between 2 to 10 angstroms, providing high MR and large PMA through anisotropy at interfaces or strain, optimized for use in magnetic tunnel junctions (MTJs).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a material is designed to exhibit high tunnel magnetoresistance with MgO tunnel barriers, then the MR is improved, but it becomes difficult to simultaneously achieve large perpendicular magnetic anisotropy (PMA)
Solution Approach 1:
The patent employs composite multilayer structures consisting of alternating BCC iron layers and BCC or amorphous cobalt layers. This composite approach allows the material to simultaneously achieve high tunnel magnetoresistance and large perpendicular magnetic anisotropy, as the combination of different magnetic materials with specific crystal structures creates synergistic effects that neither material alone can provide.
Solution Approach 2:
The magnetic material is divided into multiple thin alternating layers of iron and cobalt, each with thickness between 2 to 10 angstroms. This segmentation into ultrathin layers creates numerous interfaces that contribute to perpendicular magnetic anisotropy while maintaining the magnetic properties needed for high tunnel magnetoresistance in MgO-based tunnel junctions.
2Area of moving object
If the MTJ size is reduced to enable smaller bit reading, then the write current for magnetization reversal becomes smaller, but the write current density increases
Solution Approach 1:
The patent changes the magnetic anisotropy parameter from in-plane to perpendicular magnetic anisotropy by using alternating BCC iron and BCC or amorphous cobalt layers. This parameter change reduces the write current density required for magnetization reversal, allowing smaller MTJ areas to be used without proportionally increasing the write current density, thus enabling smaller bit reading with manageable energy requirements.
Solution Approach 2:
The patent utilizes the phase transition or structural transition between BCC and amorphous states in cobalt layers to achieve perpendicular magnetic anisotropy. This structural phase transition in the cobalt layers creates the necessary magnetic anisotropy that reduces the energy barrier for magnetization switching, thereby lowering the write current density even in reduced-size MTJs.
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 multilayer structure enhances spin torque switching efficiency by reducing the necessary write current density, enabling smaller bit reading and improving MRAM performance with high MR and large PMA, suitable for efficient data storage.
Implementation Method 1
the magnetic material has a perpendicular magnetic anisotropy (PMA)
Implementation Method 2
providing high MR and large PMA through anisotropy at interfaces or strain
Implementation Method 3
uses tunneling magnetoresistance (TMR or MR) to store information
Data Source
AI summary
A magnetic material includes a cobalt layer between opposing iron layers. The iron layers include iron and are body-centered cubic (BCC), the cobalt layer comprises cobalt and is BCC or amorphous, and the magnetic material has a perpendicular magnetic anisotropy (PMA).