Magnetoresistive Element With Nitrogen Buffer Layer
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Solution Overview
Problem
In spin-injection magnetic random access memory (MRAM) using a perpendicular magnetization film, the high damping constant of the recording layer leads to increased write current, which is proportional to the damping constant and inversely proportional to spin polarizability, necessitating a reduction in damping constant and area size to minimize write current.
Innovation Solution
A magnetoresistive element is designed with a recording layer having perpendicular magnetic anisotropy and a nitrogen compound buffer layer to reduce the damping constant, comprising a CoFe magnetic layer with a higher Fe concentration and a CoFe buffer layer with a lower Fe concentration, along with a nitride buffer layer to control nitrogen concentration and film thickness, thereby reducing the write current and enhancing the magnetoresistance ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a Ru buffer layer is used for crystal matching, then crystal structure alignment is improved, but the damping constant increases leading to larger write current
Solution Approach 1:
The patent changes the material composition of the buffer layer from pure Ruthenium to a Ru-based alloy containing at least one of Rhodium (Rh), Iridium (Ir), or Palladium (Pd). This compositional parameter change reduces the damping constant of the recording layer while maintaining crystal structure alignment, thereby reducing write current requirements.
Solution Approach 2:
The invention uses a composite buffer layer material consisting of Ruthenium combined with other transition metals (Rh, Ir, or Pd). This composite material provides both the crystal matching function of Ru and the reduced damping constant effect of the alloying elements, resolving the contradiction between structural stability and energy efficiency.
2Use of energy by moving object
If the area size of the recording layer is reduced, then write current is reduced, but the magnetoresistance ratio decreases
Solution Approach 1:
The patent optimizes the thickness parameters of multiple layers including the buffer layer, recording layer, and tunnel barrier layer. By precisely controlling these dimensional parameters, the invention achieves high magnetoresistance ratio even in reduced area devices while maintaining low write current through the reduced damping constant.
3Use of energy by moving object
If the damping constant is reduced to lower write current, then write current decreases, but record retention energy may be compromised
Solution Approach 1:
The patent carefully balances multiple parameters including buffer layer composition, recording layer thickness, and magnetic anisotropy. By optimizing these parameters together, the invention achieves reduced damping constant for lower write current while maintaining sufficient perpendicular magnetic anisotropy energy for stable record retention.
Solution Approach 2:
The use of Ru-based composite buffer layer materials provides a balance between reducing damping constant and maintaining the structural and magnetic properties necessary for record retention. The alloying elements contribute to both reduced damping and maintained magnetic stability.
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 effectively reduces the write current and improves the perpendicular magnetic characteristic and magnetoresistance ratio of the MRAM, while maintaining record retention energy and preventing magnetic anisotropy deterioration, enabling a more efficient and practical MRAM technology.
Implementation Method 1
the Ru buffer increases a damping constant of a recording layer... reduction of the damping constant... are mandatory technologies to reduce the write current
Implementation Method 2
A stacked film of Cobalt (Co) having a dense atomic plane and Platinum (Pt) has a magnetocrystalline anisotropy as high as 107 erg/cm2
Implementation Method 3
achieve a large capacity... achieve a high magnetoresistance ratio (MR ratio)
Data Source
AI summary
According to one embodiment, a magnetoresistive element includes a recording layer having a variable magnetization direction, a reference layer having an invariable magnetization direction, an intermediate layer provided between the recording layer and the reference layer, and a first buffer layer provided on a surface of the recording layer, which is opposite to a surface of the recording layer where the intermediate layer is provided. The recording layer comprises a first magnetic layer which is provided in a side of the intermediate layer and contains CoFe as a main component, and a second magnetic layer which is provided in a side of the first buffer layer and contains CoFe as a main component, a concentration of Fe in the first magnetic layer being higher than a concentration of Fe in the second magnetic layer. The first buffer layer comprises a nitrogen compound.