Spin Transfer Torque Magnetic Memory Device with Perpendicular Anisotropy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional magnetic memory devices face challenges in achieving high integration and reducing power consumption due to high critical current density and thermal instability caused by stray fields, especially as device sizes decrease.
Innovation Solution
A magnetic memory device structure incorporating a first fixed magnetic layer, a first free magnetic layer with perpendicular anisotropy, and a second free magnetic layer with horizontal anisotropy, along with non-magnetic layers, which induces an alternating current magnetic field to reduce critical current density and mitigate stray field effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the device size is reduced to achieve high integration, then the integration density is improved, but the thermal stability deteriorates due to increased influence of stray fields
Solution Approach 1:
A non-magnetic layer is inserted between the fixed magnetic layer and the free magnetic layer to act as an intermediary that blocks or reduces the stray field from the fixed layer from affecting the free layer, thereby improving thermal stability while maintaining small device dimensions for high integration
Solution Approach 2:
The stray field that was previously harmful to thermal stability is converted into a beneficial effect by using it to induce alternating current magnetic field through magnetic resonance precession in the free layer, which assists in reducing the critical current density for magnetization reversal
2Use of energy by moving object
If the critical current density is reduced to lower power consumption, then the energy efficiency is improved, but the magnetization reversal reliability worsens
Solution Approach 1:
The free layer is designed to undergo magnetic resonance precession when exposed to stray field from the fixed layer, creating periodic oscillation that reduces the critical current density required for magnetization reversal while maintaining reliable switching through resonant enhancement
Solution Approach 2:
The magnetization direction of the free layer is changed from in-plane to perpendicular orientation, and the anisotropy type is changed from shape anisotropy to perpendicular magnetic anisotropy (PMA), which fundamentally changes the magnetization reversal mechanism and enables lower critical current density with maintained reliability
3Reliability
If the free layer uses perpendicular anisotropy to improve thermal stability, then the thermal stability is improved, but the critical current density increases
Solution Approach 1:
The non-magnetic layer serves as a mediator that reduces the stray field interaction between fixed and free layers, allowing the free layer to maintain perpendicular anisotropy for thermal stability while the reduced stray field prevents excessive critical current density increase
Solution Approach 2:
The stray field that would normally increase critical current density is converted into a beneficial alternating current magnetic field through magnetic resonance precession, which actually reduces the critical current density required for magnetization reversal while preserving thermal stability
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 proposed structure effectively reduces the critical current density for magnetization reversal, enhances thermal stability, and allows for higher integration and lower power consumption without deteriorating device characteristics.
Implementation Method 1
induces an alternating current magnetic field in itself in the injection of a current by inserting a free magnetic layer having horizontal anisotropy into a free layer having perpendicular anisotropy
Implementation Method 2
A current is applied to the spin valve structure so that a current spin-polarized by the first magnetic material (a fixed magnetic layer) passes through the second magnetic material (a free magnetic layer) to transfer its spin angular momentum. This is called spin-transfer-torque.
Implementation Method 3
A giant magnetic resistance effect that an electric resistance is changed depending on relative magnetization directions of two magnetic layers occurs in a spin valve structure having a non-magnetic material inserted between two ferromagnetic bodies
Data Source
AI summary
The present invention relates to a magnetic memory device which additionally comprises a free magnetic layer constituting a horizontal direction variable magnetization layer having a fixed saturation magnetization value, whereby a switching current is markedly reduced as compared with conventional magnetic layers such that a high degree of integration of the device can be achieved and it is possible to lower a critical current density necessary for magnetization reversal thereby reducing the power consumption of the device. Also, a stray field effect occurring from a fixed magnetic layer is reduced such that a written magnetization data is thermally stable.