Magnetic Storage Device Switching Field Reduction
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Solution Overview
Problem
Magnetic storage devices with magnetoresistive elements face challenges in miniaturization, leading to variations in switching fields due to shape deformations and difficulties in maintaining consistent magnetization switching fields, especially as memory cells become smaller.
Innovation Solution
A laminated structure comprising a first magnetic body, a nonmagnetic body, and a second magnetic body, with a third magnetic body strategically positioned to reduce the switching field and minimize variations by altering the aspect ratio and magnetic coupling, allowing for easier magnetization direction changes with a smaller magnetic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the free layer is formed with a long shape (elliptic or rectangular) to utilize shape anisotropy for magnetization switching, then magnetization direction can be controlled, but the switching field becomes large and variation in switching fields increases due to shape deformation in miniaturized cells
Solution Approach 1:
A third magnetic body (auxiliary magnetic layer) is introduced as an intermediary between the first magnetic body (free layer) and the external magnetic field. This auxiliary layer has a planar shape with smaller aspect ratio than the free layer, allowing it to experience magnetization switching at lower fields and subsequently assist in switching the free layer's magnetization, thereby reducing the overall switching field while maintaining reliability
Solution Approach 2:
The aspect ratio parameter of the magnetic layer is modified by introducing a third magnetic body with different dimensional characteristics (smaller aspect ratio) compared to the first magnetic body. This parameter change allows the auxiliary layer to have different magnetic properties, specifically lower coercivity, enabling it to switch at smaller fields and transfer this advantage to the free layer
2Productivity
If memory cells are miniaturized to increase storage capacity, then device density improves, but variation in free layer shapes increases making it difficult to maintain consistent switching fields
Solution Approach 1:
Different magnetic bodies are assigned different local qualities in terms of shape and magnetic properties. The third magnetic body has a planar shape specifically designed with smaller aspect ratio than the first magnetic body, creating local variation in magnetic characteristics that compensates for manufacturing variations in the free layer shape, thereby maintaining consistent switching fields across miniaturized cells
Solution Approach 2:
The magnetic storage element is constructed as a composite structure with multiple magnetic bodies (first, second, and third magnetic bodies) having different shape characteristics. This composite approach combines the advantages of each layer: the free layer provides storage functionality while the auxiliary layer with smaller aspect ratio provides robustness against shape variation, achieving consistent performance in miniaturized devices
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 switching field and minimizes variations in switching fields, enabling more reliable and efficient data storage by ensuring consistent magnetization direction changes with reduced power consumption.
Implementation Method 1
The first magnetic body and the third magnetic body are magnetically coupled
Implementation Method 2
A shape of a plane of the aforementioned free layer, a shape that is long in one direction such as an elliptic shape and a rectangular shape is generally used. In such a shape that is long in one direction, an axis into which magnetization is easy, i.e. an easy axis, is formed in the long direction due to shape anisotropy of a magnetic body
Implementation Method 3
a structure called Tunneling Magnetroregistance (hereinafter referred to as TMR) in which a tunnel insulating film is put between two magnetic bodies
Data Source
AI summary
A magnetic storage device includes a laminated structure and a third magnetic body. The laminated structure includes a first magnetic body, a nonmagnetic body, and a second magnetic body which are laminated. The third magnetic body is provided at any of a first magnetic body side and a second magnetic body side. Resistance of the laminated structure is changed based on a difference between magnetization directions of the first magnetic body and the second magnetic body. A projection of the third magnetic body onto the first magnetic body at least partly overlaps the first magnetic body. The first magnetic body and the third magnetic body are magnetically coupled. A planar shape of the first magnetic body is a shape that is long in a first direction. A length of the third magnetic body is shorter than a length of the first magnetic body in the first direction. An aspect ratio of a length of a long-axis direction of the planar shape of the first magnetic body divided by a length of a short-axis direction is greater than an aspect ratio of a length of a long-axis direction of a planar shape of the third magnetic body divided by a length of a short-axis direction.