Composite Free Layer MTJ for Low Switching Voltage
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Solution Overview
Problem
Conventional magnetic memory devices face challenges in achieving low switching voltage while maintaining thermal stability, as increasing thermal stability often makes the device harder to switch, and making it easier to switch reduces thermal stability.
Innovation Solution
The implementation of a composite free layer with a cascade switching effect and the addition of a ferromagnetic layer with a weakly out-of-plane magnetization, along with a pseudo-dual junction configuration, reduces the switching voltage without compromising thermal stability by facilitating easier switching through spin currents and coupling fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If thermal stability is increased in conventional pMTJ devices, then data retention is improved, but switching voltage increases making the device harder to switch
Solution Approach 1:
The free layer is divided into multiple sub-layers with different magnetization directions and switching characteristics. The first free layer has in-plane magnetization and switches at lower voltage, while the second free layer has perpendicular magnetization and provides thermal stability. This segmentation allows the device to achieve both low switching voltage and high thermal stability by switching layers in sequence rather than requiring high voltage to switch a single high-stability layer.
2Use of energy by moving object
If the device is made easier to switch, then switching voltage is reduced, but thermal stability deteriorates
Solution Approach 1:
The free layer is segmented into multiple sub-layers where the first sub-layer is designed to switch easily at low voltage while the second sub-layer maintains high thermal stability. This allows the device to switch at low voltage without sacrificing overall thermal stability.
Solution Approach 2:
The patent uses a composite free layer structure combining materials with different magnetic properties - the first free layer uses materials optimized for low switching voltage (in-plane magnetization), while the second free layer uses materials optimized for thermal stability (perpendicular magnetization). This composite structure achieves both low switching voltage and high thermal stability simultaneously.
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 approach results in magnetic memory devices that operate with lower switching voltage and higher thermal stability, enabling more efficient and reliable data storage with reduced power consumption and extended memory retention.
Implementation Method 1
Due to the spin-polarized electron tunneling effect, the electrical resistance of the cell changes due to the orientation of the magnetization of the two layers
Implementation Method 2
coupling fields between the FM and the storage layer are configured to further facilitate switching of the storage layer once the FM has switched
Data Source
AI summary
The various embodiments described herein include methods, devices, and systems for fabricating and performing operations on magnetic memory devices. In one aspect, a magnetic memory device includes: (1) a reference magnetic layer configured to have a first current threshold corresponding to a spin current level required to change a magnetic polarization of the reference magnetic layer; (2) a composite magnetic layer comprising a plurality of non-magnetic layers and a plurality of magnetic layers including a storage layer; and (3) a non-magnetic spacer layer between the reference magnetic layer and the composite magnetic layer; where the composite magnetic layer is configured such that the second current threshold is lowered, without decreasing thermal stability of the magnetic memory device, by spin current and/or coupling fields between adjacent magnetic layers of the plurality of magnetic layers.