Ferromagnetic Memory Cell with Anisotropy Gradient for Multi-Level Storage
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Solution Overview
Problem
Existing spin-transfer torque magnetoresistive random-access memory (STT-MRAM) devices struggle to implement multiple levels of data storage due to limitations in controlling magnetization states within a single transistor and magnetic tunnel junction (MTJ).
Innovation Solution
A ferromagnetic memory device is developed with a magnetic anisotropy energy gradient induced by plasma ion irradiation, forming multiple magnetic domains within the magnetic free layer, and controlled through varying input current pulses to manage magnetization states across these domains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single magnetic tunnel junction (MTJ) is used for data storage, then the device structure is simple, but only one bit of data can be stored
Solution Approach 1:
The magnetic free layer is divided into multiple magnetic domains (first, second, and third magnetic domains) with different magnetization states. Each domain can independently store one bit of data, enabling multi-bit storage capacity while maintaining a single MTJ structure. The segmentation is achieved through controlled ion irradiation that creates distinct magnetic regions within the free layer.
Solution Approach 2:
Different regions of the magnetic free layer are given different magnetic properties through selective ion irradiation. The first, second, and third magnetic domains have different magnetization directions and switching characteristics, allowing each region to serve a specific storage function. This local differentiation enables multi-level storage without requiring multiple separate MTJ cells.
2Quantity of substance
If multiple magnetic domains are formed in the magnetic free layer, then multi-bit data storage is enabled, but the manufacturing process becomes more complex
Solution Approach 1:
The magnetic domains are pre-formed during the manufacturing process through controlled ion irradiation before the device is put into service. By establishing the multi-domain structure during fabrication, the complexity is front-loaded into manufacturing rather than requiring complex control circuits or post-processing steps during operation. The ion irradiation pattern is designed in advance to create the desired domain configuration.
3Adaptability or versatility
If ion irradiation is used to create magnetic anisotropy energy gradient, then multiple magnetic domains are formed, but the manufacturing process requires additional steps
Solution Approach 1:
The manufacturing process utilizes ion irradiation to change the magnetic parameters (anisotropy energy, magnetization direction) of different regions within the magnetic free layer. By controlling the ion irradiation conditions (energy, angle, pattern), distinct magnetic domains with different properties are created, enabling multi-level operation. This parameter modification approach allows versatile functionality to be achieved through a relatively simple additional manufacturing step compared to creating multiple separate MTJ structures.
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
Enables the ferromagnetic memory device to operate at multiple levels by adjusting the magnetization state of each domain, allowing for efficient multi-bit data storage and retrieval.
Implementation Method 1
a magnetic anisotropy energy gradient induced within the magnetic layer by plasma ion irradiation
Implementation Method 2
plasma ion irradiation
Implementation Method 3
Ferromagnetic materials are easily magnetized and maintain their magnetization states even after an external magnetic field is removed
Data Source
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AI summary
A ferromagnetic memory device is disclosed. The ferromagnetic memory device comprising a memory cell, wherein the memory cell includes a magnetic free layer including a magnetic layer, and wherein the magnetic free layer including a magnetic anisotropy energy gradient induced within the magnetic layer by plasma ion irradiation.