Magnetic Memory Device With Non-Magnetic Interface Layer
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Solution Overview
Problem
Magnetic memory devices, such as MRAM, face challenges in miniaturization due to leakage magnetic fields and heat stability issues, particularly when using materials with high saturation magnetization, which can lead to interference between adjacent cells and instability during read/write operations.
Innovation Solution
Incorporating a non-magnetic material like molybdenum (Mo) into the interface layer of the magnetic tunnel junction (MTJ) element, with a concentration gradient from the tunnel barrier layer towards the reference layer, to lower saturation magnetization and enhance heat stability while maintaining a high magneto-resistance ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If materials with high saturation magnetization are used in magnetic memory devices, then the magnetic signal strength is improved, but leakage magnetic fields increase causing interference between adjacent cells
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of non-magnetic atoms within the magnetic layer. The concentration of non-magnetic atoms increases from the bottom interface toward the top interface of the magnetic layer, resulting in different local magnetic properties. This gradient structure reduces the saturation magnetization locally at the interfaces where leakage fields are generated, thereby suppressing interference between adjacent memory cells while maintaining adequate magnetic signal strength in the bulk of the layer.
Solution Approach 2:
The patent changes the magnetic parameters of the magnetic layer by controlling the concentration and distribution of non-magnetic atoms. By adjusting the concentration gradient of non-magnetic atoms (such as Mo, Ta, W, Hf, Nb, or Ti) in the magnetic layer, the saturation magnetization can be optimized to achieve a balance between signal strength and leakage field suppression. This parameter change allows the device to operate with reduced interference while maintaining functionality.
2Quantity of substance
If the magnetic layer is miniaturized to increase storage density, then the storage capacity is improved, but heat stability deteriorates due to reduced heat stability energy
Solution Approach 1:
The patent applies local quality by creating distinct regions within the magnetic layer with different non-magnetic atom concentrations. The regions closer to the interfaces have higher concentrations of non-magnetic atoms, which modify the local magnetic anisotropy and reduce magnetization. This local modification helps maintain heat stability in miniaturized structures by creating energy barriers that prevent thermal fluctuations from causing unwanted magnetization reversal, thereby improving reliability in small-scale devices.
3Object-generated harmful factors
If non-magnetic materials are added to reduce saturation magnetization, then leakage magnetic fields are suppressed, but the magneto-resistance ratio may degrade
Solution Approach 1:
The patent applies local quality by concentrating non-magnetic atoms preferentially at the interfaces of the magnetic layer rather than uniformly distributing them throughout. This localized distribution suppresses leakage magnetic fields at the critical interface regions where adjacent cell interference occurs, while preserving the magnetic properties and magneto-resistance ratio in the bulk of the magnetic layer. The gradient structure ensures that the majority of the magnetic layer maintains its ferromagnetic characteristics necessary for high MR ratio.
Solution Approach 2:
The patent employs composite materials by combining magnetic material with non-magnetic atoms (such as Mo, Ta, W, Hf, Nb, or Ti) in a controlled gradient structure. This composite approach creates a material system where the magnetic phase provides the necessary magnetization and magneto-resistance, while the non-magnetic components locally reduce saturation magnetization to suppress leakage fields. The composite structure optimizes both contradictory requirements by spatially separating the functions of different material components.
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 configuration improves the reliability of magnetic memory devices by reducing interference between cells, suppressing leakage magnetic fields, and maintaining high heat stability without degrading the MR ratio, thus ensuring reliable data storage and operation.
Implementation Method 1
a non-magnetic layer including at least one of No (molybdenum), Ta (tantalum), W (tungsten), Hf (hafnium), Nb (niobium), and Ti (titanium)
Implementation Method 2
A magnetic memory device includes a first magnetic layer having a variable magnetization direction, a first non-magnetic layer provided on the first magnetic layer, and a second magnetic layer provided on the first magnetic layer and having a fixed magnetization direction
Data Source
AI summary
According to one embodiment, a magnetic memory device includes a first magnetic layer having a variable magnetization direction, a first non-magnetic layer provided on the first magnetic layer, and a second magnetic layer provided on the first magnetic layer and having a fixed magnetization direction and provided on the first magnetic layer. The second magnetic layer includes a non-magnetic metal including at least one of Mo (molybdenum), Ta (tantalum), W (tungsten), Hf (hafnium), Nb (niobium) and Ti (titanium).