TbCoFe Magnetic Film Heat Resistance via Ta Interlayer
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Solution Overview
Problem
The amorphous TbCoFe film used in magnetoresistive effect elements has low heat resistance, limiting the effectiveness of heat treatment for improving element characteristics due to its low perpendicular magnetic anisotropy, which restricts the enhancement of magnetoresistive effect element performance.
Innovation Solution
Incorporating amorphous phases and crystals with particle sizes of 0.5 nm or more in the magnetic film, specifically in the TbCoFe film, which maintains perpendicular magnetic anisotropy even at high temperatures, and using a Ta film in the interface layer to prevent crystallization and diffusion, thereby enhancing heat resistance and element characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat treatment is applied to improve element characteristics, then tunnel barrier layer crystallization is enhanced, but amorphous TbCoFe film crystallizes causing deterioration of perpendicular magnetic anisotropy
Solution Approach 1:
An amorphous protective film is introduced between the tunnel barrier layer and the amorphous TbCoFe film. This protective film acts as a barrier that prevents heat transfer to the TbCoFe film during heat treatment, thereby protecting it from crystallization while allowing the tunnel barrier layer to be properly crystallized. The protective film serves as a thermal buffer that mediates the conflicting requirements of heat treatment for the tunnel barrier versus heat protection for the magnetic film.
Solution Approach 2:
The invention changes the thermal parameters by controlling the heat treatment temperature and duration to be sufficient for tunnel barrier layer crystallization but insufficient to cause crystallization of the amorphous TbCoFe film. By carefully adjusting these parameters and using the protective film as a thermal barrier, the system achieves differential thermal treatment where different layers experience different effective temperatures, allowing the tunnel barrier to crystallize while the magnetic film remains amorphous.
2Reliability
If saturation magnetization of reference layer is reduced for switching field adjustment, then magnetic performance is improved, but heat resistance of perpendicular magnetic anisotropy deteriorates
Solution Approach 1:
The amorphous protective film serves as a thermal protective barrier that mediates between the reduced heat resistance of the amorphous TbCoFe film and the high-temperature heat treatment process. This protective layer allows the system to maintain the low saturation magnetization benefits while compensating for the poor heat resistance through the intermediary protective film that prevents thermal damage during processing.
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 approach improves the heat resistance and element characteristics of magnetoresistive effect elements, allowing for effective high-temperature processing without deteriorating magnetic properties, resulting in enhanced performance and reliability.
Implementation Method 1
a first magnetic layer including perpendicular anisotropy to a film surface and an invariable magnetization direction, the first magnetic layer having a magnetic film including an element selected from a first group including Tb, Gd, and Dy and an element selected from a second group including Co and Fe
Implementation Method 2
the magnetic film includes amorphous phases and crystals whose particle sizes are 0.5 nm or more
Data Source
AI summary
According to one embodiment, a magnetoresistive effect element includes a first magnetic layer including perpendicular anisotropy to a film surface and an invariable magnetization direction, the first magnetic layer having a magnetic film including an element selected from a first group including Tb, Gd, and Dy and an element selected from a second group including Co and Fe, a second magnetic layer including perpendicular magnetic anisotropy to the film surface and a variable magnetization direction, and a nonmagnetic layer between the first magnetic layer and the second magnetic layer. The magnetic film includes amorphous phases and crystals whose particle sizes are 0.5 nm or more.