Magnetoresistive Element with W Buffer Layer
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Solution Overview
Problem
Conventional magnetoresistive elements with perpendicular magnetic anisotropy face challenges in maintaining high magnetic anisotropy energy as the film thickness of the CoFeB layer increases, leading to reduced retention properties and increased series resistance due to the high resistance of the MgO layer acting as parasitic resistance.
Innovation Solution
The use of a W or Ti buffer layer with an oxygen-deficient MgO layer as the underlying layer, which reduces series resistance and allows for sufficient perpendicular magnetic anisotropy generation, even at increased film thicknesses, by leveraging interface magnetic anisotropy from both sides of the storage layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the film thickness of the CoFeB layer is increased, then the perpendicular magnetic anisotropy energy is improved, but the series resistance increases due to the high resistance of the MgO layer
Solution Approach 1:
A W or Ti buffer layer is introduced as an intermediary between the MgO underlying layer and the CoFeB storage layer. This buffer layer serves as a mediator that reduces the series resistance of the MgO layer while preserving the perpendicular magnetic anisotropy energy, thereby resolving the contradiction between improving magnetic anisotropy and reducing resistance.
Solution Approach 2:
The patent changes the physical and chemical parameters of the MgO layer by creating an oxygen-deficient state through controlled oxidation of the W or Ti buffer layer. This parameter change (oxygen concentration) reduces the resistance of the MgO layer, allowing for increased CoFeB film thickness without proportionally increasing series resistance.
2Reliability
If the film thickness of the CoFeB layer is increased, then the magnetoresistance ratio is improved, but the retention properties deteriorate
Solution Approach 1:
The W or Ti buffer layer acts as an intermediary that enables the CoFeB layer to achieve greater thickness while maintaining perpendicular magnetic anisotropy. This mediator allows the system to simultaneously improve magnetoresistance ratio (through increased thickness) and maintain retention properties (through preserved magnetic anisotropy).
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
This approach maintains high perpendicular magnetic anisotropy energy and improves retention properties by reducing the series resistance and increasing the film thickness of the storage layer, enhancing the magnetoresistance ratio and overall performance of the magnetoresistive element.
Implementation Method 1
by leveraging interface magnetic anisotropy from both sides of the storage layer
Implementation Method 2
magnetoresistive elements including a ferromagnetic tunneling junction have been gaining attention since such magnetoresistive elements were discovered to exhibit a high magnetoresistance rate
Implementation Method 3
A perpendicular magnetization film, which includes an axis of easy magnetization in a direction perpendicular to a film plane, has been considered to be used as a ferromagnetic material forming the magnetoresistive element
Data Source
AI summary
A magnetoresistive element includes first and magnetic layers, first and second non-magnetic layers and a W layer. Each of the first and second magnetic layers includes an axis of easy magnetization in a direction perpendicular to a film plane. The first magnetic layer has a variable magnetization direction. The second magnetic layer has an invariable magnetization direction. The first non-magnetic layer is provided between the first and second magnetic layers. The second non-magnetic layer is arranged on a surface of the first magnetic layer opposite to a surface on which the first non-magnetic layer is arranged and contains MgO. The W layer is arranged on a surface of the second non-magnetic layer opposite to a surface on which the first magnetic layer is arranged, and is in contact with the surface of the second non-magnetic layer.