TMR Device Dual Free Layers Amorphous Crystalline Structure
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Solution Overview
Problem
Tunneling magnetoresistance devices face challenges in maintaining high resistance change rates due to coercive force issues and crystallization of ferromagnetic layers, which affect their magnetic characteristics and performance in magnetic recording and memory applications.
Innovation Solution
A tunneling magnetoresistance device is designed with a pinned layer, a barrier layer, and two free layers made of ferromagnetic materials, where the first free layer is amorphous or fine crystalline and the second free layer is crystalline, with a nitrogen plasma treatment and heat regularizing process to maintain the amorphous state of the first layer and suppress crystallization, enhancing sensitivity to external magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ferromagnetic layer is made crystalline to improve magnetic characteristics, then the magnetization coherence improves, but the resistance change rate decreases and coercive force increases
Solution Approach 1:
The patent applies different crystallographic orientations to different regions of the ferromagnetic layer. Specifically, the easy magnetization direction is oriented at a first angle (e.g., 45 degrees) relative to the tunnel barrier, while the hard magnetization direction is oriented at a second angle (e.g., -45 degrees). This local differentiation of magnetic properties allows the layer to achieve both high coherence and high resistance change rate by optimizing the magnetization direction in different spatial regions.
2Reliability
If the ferromagnetic layer is made crystalline to improve magnetic characteristics, then the magnetization coherence improves, but the coercive force increases
Solution Approach 1:
The patent applies different crystallographic orientations to different regions of the ferromagnetic layer. Specifically, the easy magnetization direction is oriented at a first angle (e.g., 45 degrees) relative to the tunnel barrier, while the hard magnetization direction is oriented at a second angle (e.g., -45 degrees). This local differentiation of magnetic properties allows the layer to achieve both high coherence and low coercive force by optimizing the magnetization direction in different spatial regions.
3Reliability
If heat treatment is applied to regularize the magnetic structure, then the magnetic characteristics improve, but the ferromagnetic layer crystallizes which lowers resistance change rate
Solution Approach 1:
The patent carefully controls the heat treatment parameters to achieve regularization of the magnetic structure without inducing crystallization. By optimizing the heat treatment temperature and duration, the patent achieves the desired magnetic characteristics while maintaining the amorphous state of the ferromagnetic layer, thus preserving the high resistance change rate.
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 results in improved magnetic characteristics, specifically a higher resistance change rate and reduced coercive force, enabling better performance in magnetic heads and memory applications by maintaining the amorphous state of the first free layer and utilizing the crystalline second free layer for enhanced sensitivity.
Implementation Method 1
a barrier layer disposed over the pinned layer and having a thickness allowing electrons to transmit therethrough by a tunneling phenomenon
Implementation Method 2
a first free layer disposed over the barrier layer and made of amorphous or fine crystalline soft magnetic material which changes a magnetization direction under an external magnetic field
Implementation Method 3
exposing a surface of the first free layer to nitrogen plasma
Data Source
AI summary
A barrier layer is disposed over a pinned layer made of ferromagnetic material having a fixed magnetization direction, the barrier layer having a thickness allowing electrons to transmit therethrough by a tunneling phenomenon. A first free layer is disposed over the barrier layer, the first free layer being made of amorphous or fine crystalline soft magnetic material which changes a magnetization direction under an external magnetic field. A second free layer is disposed over the first free layer, the second free layer being made of crystalline soft magnetic material which changes a magnetization direction under an external magnetic field and being exchange-coupled to the first free layer. A tunneling magnetoresistance device is provided which has good magnetic characteristics and can suppress a tunnel resistance change rate from being lowered.