Magnetic Cell With Orthogonal Reference Layers
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Solution Overview
Problem
Spin torque transfer memory cells face a dilemma between low switching current and data stability, with high switching current densities making integration with CMOS processes difficult and affecting data retention due to thermal instability.
Innovation Solution
The design of magnetic cells with two reference layers having orthogonal magnetization orientations, including a free magnetic layer between oxide barrier layers, allows for quick switching between high and low resistance states, improving write speed and tunneling magneto-resistance ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spin torque transfer memory cells use conventional single reference layer design, then data stability is maintained, but switching current density is high (10^6 to 10^7 A/cm^2) making CMOS integration difficult
Solution Approach 1:
The patent divides the single reference layer into two separate reference layers with orthogonal magnetization orientations. This segmentation allows the free layer to switch between two stable states defined by orthogonal reference directions, reducing the switching current density while maintaining data stability through the orthogonal magnetization configuration.
Solution Approach 2:
The patent introduces a new dimension by using orthogonal magnetization orientations in the reference layers rather than parallel or antiparallel arrangements. This dimensional change in magnetization space enables lower switching currents while preserving thermal stability and data retention.
2Use of energy by moving object
If spin torque transfer cells reduce switching current for lower power, then data retention deteriorates due to thermal instability
Solution Approach 1:
By segmenting the reference structure into two orthogonally oriented reference layers, the patent creates two independent energy barriers for the free layer magnetization. This segmentation provides dual stability references that maintain data retention even at reduced switching currents, overcoming the thermal instability issue.
Solution Approach 2:
The patent employs a composite magnetic structure combining multiple ferromagnetic layers with orthogonal magnetization orientations. This composite configuration creates enhanced thermal stability through the orthogonal arrangement, allowing reduced switching currents without compromising data retention.
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 design reduces switching current density while maintaining data stability, enhancing the integration of spin torque memory cells with CMOS processes and improving data retention.
Implementation Method 1
The resistance of the magnetic element depends on the moment's alignment or orientation. The stored state is read from the element by detecting the component's resistive state.
Implementation Method 2
Spin torque transfer technology, also referred to as spin electronics, combines semiconductor technology and magnetics, and is a more recent development. In spin electronics, the spin of an electron, rather than the charge, is used to indicate the presence of digital information.
Data Source
AI summary
A magnetic cell includes a ferromagnetic free layer having a free magnetization orientation direction and a first ferromagnetic pinned reference layer having a first reference magnetization orientation direction that is parallel or anti-parallel to the free magnetization orientation direction. A first oxide barrier layer is between the ferromagnetic free layer and the first ferromagnetic pinned reference layer. The magnetic cell further includes a second ferromagnetic pinned reference layer having a second reference magnetization orientation direction that is orthogonal to the first reference magnetization orientation direction. The ferromagnetic free layer is between the first ferromagnetic pinned reference layer and the second ferromagnetic pinned reference layer.