Cryogenic Memory Cell Combining Spin Transfer and Nano-SQUID Readout
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Solution Overview
Problem
Current memory devices for superconducting electronics face challenges such as limited storage capacity, low write speed, high power consumption, and incompatibility with Rapid Single Flux Quantum (RSFQ) signals.
Innovation Solution
The proposed solution involves a cryogenic memory cell comprising a spin moment transfer device and a nano-superconducting quantum interference device (nano-SQUID), which convert write currents into spin polarization currents and magnetic flux changes, respectively, to achieve write and read operations compatible with RSFQ signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If cryogenic semiconductor memories use elements with large resistance to achieve characteristic voltage of about 1V, then the operating voltage is improved, but power consumption increases
Solution Approach 1:
The patent changes the resistance parameter of the spin moment transfer device to a low resistance range (1-10 ohms), fundamentally different from conventional high-resistance elements. This parameter change enables operation at characteristic voltages of 1V or less while reducing power consumption, as the low resistance allows sufficient current flow without requiring high voltage drops.
2Productivity
If the feature size of spin moment transfer device is reduced to less than or equal to 100 nm, then integration density is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent transitions from planar two-dimensional structures to three-dimensional stacked structures (fixed magnet-containing layer, metal layer, and free magnetic layer stacked in sequence). This dimensional change allows the device to achieve high integration density through vertical stacking while maintaining manufacturable feature sizes, as the stack architecture can be fabricated using standard spin-coating and annealing processes without requiring extreme precision at the 100 nm scale.
3Reliability
If a superconducting ring with Josephson junction is used to latch flux quanta, then storage of 0 and 1 is achieved, but integration of superconducting circuit is limited
Solution Approach 1:
The patent extracts the magnetic moment reversal function from complex superconducting ring structures with Josephson junctions and implements it using a simplified spin moment transfer device based on spin-polarized current. This extraction eliminates the need for complex superconducting circuits while maintaining the essential data storage capability through magnetic moment reversal, thereby significantly improving integration density.
4Speed
If RSFQ circuits use single-flux voltage pulses with picosecond pulse width, then operating frequency is improved, but storage capacity of memory composed of RSFQ circuits is limited
Solution Approach 1:
The patent merges the high-speed readout capability of superconducting nano-SQUID devices with the high-density storage capability of spin moment transfer devices. The nano-SQUID provides picosecond-scale readout speed compatible with RSFQ circuits, while the spin moment transfer device enables high-density storage through its compact stacked structure. This combination achieves both high operating frequency and large storage capacity 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 reduces power consumption, increases write speed, and enables high-density integration, thereby achieving high-capacity storage compatible with RSFQ circuits.
Implementation Method 1
the spin moment transfer device converts the write current into a spin polarization current and changes a magnetic polarization direction under the action of the spin polarization current to achieve write storage of 0 and 1
Implementation Method 2
the nano-superconducting quantum interference device undergoes a magnetic flux change under the action of a change in the magnetic polarization direction of the spin moment transfer device
Implementation Method 3
thereby switching between a superconducting state and a non-superconducting state under a read current bias
Implementation Method 4
use Josephson junctions (JJ) as basic elements. RSFQ circuits have overall power consumption of a few milliwatts and an operating frequency up to nearly 100 GHz
Data Source
AI summary
A cryogenic memory cell and a memory device are provided. The cryogenic memory cell includes a spin moment transfer device. The spin moment transfer device converts a write current into a spin polarization current and changes a magnetic polarization direction under the action of the spin polarization current to achieve write storage of 0 and 1. The cryogenic memory cell also includes a nano-superconducting quantum interference device; a ground terminal of the nano-superconducting quantum interference device is in common-ground connection with a ground terminal of the spin moment transfer device, and the nano-superconducting quantum interference device undergoes a magnetic flux change under the action of a change in the magnetic polarization direction of the spin moment transfer device, thereby switching between a superconducting state and a non-superconducting state under a read current bias, to achieve read-out of 0 and 1.