Spin Transfer Torque Device Oxide Layer Seed Damping
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Solution Overview
Problem
In spin transfer torque (STT) devices, the damping effect caused by spin pumping from the metal or metal alloy seed layer to the free layer hinders the oscillation of the free layer's magnetization, requiring an increase in the DC critical current to initiate oscillation, which is not feasible when the seed layer is in direct contact with the free layer to ensure proper crystalline growth.
Innovation Solution
Incorporating an intermediate oxide layer between the write pole and the free layer, and a nonmagnetic electrically conducting buffer layer between the write pole and the intermediate oxide layer, to reduce the damping effect by reflecting spin current and removing spin polarization, respectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the seed layer is in direct contact with the free layer to ensure proper crystalline growth, then the crystalline structure is improved, but the damping effect increases requiring higher DC critical current
Solution Approach 1:
An oxide layer is introduced as an intermediary between the metal seed layer and the free layer. This oxide layer serves as a buffer that reduces spin pumping from the seed layer while still allowing the seed layer to provide proper crystalline template for the free layer growth, thus resolving the contradiction between maintaining crystalline structure and reducing damping effect.
2Use of energy by moving object
If the oxide layer is placed between the write pole and the free layer, then the damping effect is reduced, but the device complexity increases
Solution Approach 1:
The oxide layer is positioned to serve multiple functions simultaneously: it acts as a buffer to reduce spin pumping damping, provides a suitable interface for seed layer deposition, and maintains structural integrity of the spin valve. This multi-functionality reduces the need for additional separate layers, thereby limiting the increase in device complexity.
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 intermediate oxide layer reduces the damping effect on the free layer's magnetization oscillation, allowing for a lower DC critical current to initiate oscillation, while maintaining the proper crystalline structure and performance of the STT device.
Implementation Method 1
the damping effect caused by spin pumping from the metal or metal alloy seed layer to the free layer
Implementation Method 2
Spin transfer torque (STT) is an effect in which the orientation of the magnetization of a magnetic layer in a magnetic tunnel junction (MTJ) or giant magnetoresistance (GMR) spin valve can be modified using a spin-polarized current
Implementation Method 3
a nonmagnetic electrically conducting buffer layer between the write pole and the intermediate oxide layer, to reduce the damping effect by reflecting spin current and removing spin polarization, respectively
Data Source
AI summary
A spin transfer torque (STT) device is formed on an electrically conductive substrate and includes a ferromagnetic free layer near the substrate, a ferromagnetic polarizing layer and a nonmagnetic spacer layer between the free layer and the polarizing layer. A multilayer structure is located between the substrate and the free layer. The multilayer structure includes a metal or metal alloy seed layer for the free layer and an intermediate oxide layer below and in contact with the seed layer. The intermediate oxide layer reflects spin current from the free layer and thus reduces undesirable damping of the oscillation of the free layer's magnetization by the seed layer.