Superconducting Memory Cell with Magnetic Junction
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Solution Overview
Problem
Existing hybrid superconducting and magnetic memory cells face challenges in achieving high access speed, small size, high integration density, and low power consumption while efficiently operating in digital superconducting circuits, with previous designs struggling to scale down effectively and maintain magnetic field-induced critical current suppression.
Innovation Solution
A memory cell design featuring a superconductive Josephson junction and a magnetic junction vertically integrated in close proximity, with the magnetic junction comprising two magnetic layers of different coercive forces and a non-magnetic layer, allowing for controlled magnetization rotation and significant critical current variation, enabling efficient logic states representation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional SFQ memory cells are used, then low energy dissipation is achieved, but large area is required due to superconducting loops
Solution Approach 1:
The patent combines superconducting Josephson junctions with magnetic memory elements into a hybrid structure, merging the low-power advantages of superconducting circuits with the compactness of magnetic memory, thereby reducing both energy dissipation and chip area simultaneously
Solution Approach 2:
The memory cell uses composite structures combining superconducting materials (for low-energy operation) and magnetic materials (for compact storage), allowing the system to achieve both low power consumption and high density in a single integrated device
2Adaptability or versatility
If magnetic Josephson junctions are used, then critical current can be tuned, but device complexity increases due to hysteresis
Solution Approach 1:
The patent introduces local magnetic fields through patterned magnetic layers or external field application at specific locations, enabling precise control of critical current in individual junctions without requiring complex global control mechanisms, thus maintaining simplicity while achieving tunability
3Productivity
If vertically integrated structure is used, then integration density is improved, but manufacturing precision requirements increase
Solution Approach 1:
The vertically integrated memory cell is divided into distinct functional layers (superconducting layers, magnetic layers, insulating layers) that can be fabricated separately using standard thin-film deposition techniques, then assembled through aligned deposition, reducing the overall manufacturing precision requirement compared to monolithic vertical structures
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 memory cell achieves high access speed, small size, and low power consumption, with a critical current variation of at least 15% between logic states, facilitating efficient operation in high-density memory arrays and enabling reliable READ and WRITE operations.
Implementation Method 1
Superconducting electronic circuits comprise Josephson junctions as the basic constituent elements
Implementation Method 2
a magnetic field applied in the plane of the JJ will modulate the critical current Ic according to a sine function dependence
Implementation Method 3
Because the barrier of an MJJ contains a ferromagnetic material, which being a permanent magnet material has hysteresis, the stable magnetic flux in the junction may have (at least) two different values
Implementation Method 4
produce very fast low-voltage pulses when the junctions switch from the superconductive to the resistive state and back again
Data Source
AI summary
A memory cell having a Josephson junction and a magnetic junction situated in a close proximity to the Josephson junction. The two junctions may be vertically integrated. The magnetic junction has at least two magnetic layers with different coercive forces and a non-magnetic layer therebetween, to form a spin valve or pseudo-spin valve. A magnetization direction of a magnetic layer with lower coercive force can be rotated with respect to the larger coercive force magnetic layer(s). Magnetic fields produced by appropriately configured control lines carrying electric current, or spin-polarized current through the magnetic junction, can result in rotation. The magnetic junction influences the Josephson critical current of the Josephson junction, leading to distinct values of critical current which can serve as digital logic states. The so obtained memory cell can be integrated into the large arrays containing a plurality of the cells, to enable the selective READ and WRITE operations.