Magnetic Domain Wall Propagation via Spin Transfer Torque
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Solution Overview
Problem
Existing magnetic domain wall memory devices require external magnetic fields to generate and propagate domain walls, which is inefficient and difficult to scale down, and introduces variability and increased costs due to complex process steps.
Innovation Solution
A method to generate a stream of domain walls along a magnetic bus without an external magnetic field by using a device with a magnetic propagation layer featuring converging magnetic buses, where spin orbit torques and spin transfer torques are applied to a pinned domain wall to alternate its configuration, allowing for efficient propagation and data recording.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If external magnetic fields are used to generate and propagate domain walls, then domain wall motion can be achieved, but the current required is relatively large and scaling down becomes difficult
Solution Approach 1:
The patent replaces the mechanical approach of using external magnetic fields to move domain walls with a spintronic approach using spin transfer torque. Instead of applying Oersted fields from external magnets, the invention uses spin-polarized current flowing through a ferromagnetic layer to exert torque on the magnetization, thereby propagating domain walls with much lower current consumption.
Solution Approach 2:
The patent changes the fundamental parameter for domain wall propagation from magnetic field strength to spin transfer torque efficiency. By using a ferromagnetic layer with specific magnetic properties (saturation magnetization, perpendicular magnetic anisotropy) and controlling the spin polarization of the current, the system achieves domain wall motion at significantly reduced current levels compared to external magnetic field approaches.
2Speed
If external magnetic fields are used to generate domain walls, then domain wall motion can be achieved, but process complexity and variability increase
Solution Approach 1:
The patent extracts and eliminates the need for external magnetic field generation components (magnets, magnetic field coils) from the device architecture. By confining the domain wall generation and propagation mechanism entirely within the spintronic stack using spin transfer torque, the invention removes the complex external field generation infrastructure and associated process steps.
Solution Approach 2:
The ferromagnetic layer serves multiple functions: it stores magnetic domains, generates domain walls through spin transfer torque, and propagates them along the magnetic bus. This multi-functionality eliminates the need for separate external magnetic field generation systems, simplifying the overall device structure and reducing process complexity.
3Speed
If external magnetic fields are used to generate domain walls, then domain wall motion can be achieved, but device scaling becomes difficult
Solution Approach 1:
The patent replaces the mechanical external magnetic field generation system with a nanoscale spintronic structure that can be integrated into standard semiconductor fabrication processes. The spin transfer torque mechanism operates at the nanoscale within the magnetic tunnel junction stack, enabling continuous scaling to smaller dimensions without the physical constraints of external magnetic field sources.
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 enables low-current, energy-efficient generation and propagation of domain walls, allowing for improved scalability and reduced variability, as well as the ability to reuse initialized domain walls for improved energy efficiency and low-current implementation.
Implementation Method 1
a spin-polarized current is applied to a ferromagnetic layer such that a spin transfer torque is applied to a magnetization of the ferromagnetic layer
Implementation Method 2
The ferromagnetic layer has a perpendicular magnetic anisotropy
Data Source
AI summary
The disclosed technology generally relates to magnetic devices, and more particularly to magnetic devices configured to generate a stream of domain walls propagating along an output magnetic bus. In an aspect, a magnetic device includes a magnetic propagation layer, which in turn includes a plurality of magnetic buses. The magnetic buses include at least a first magnetic bus, a second magnetic bus, and an output magnetic bus configured to guide propagating magnetic domain walls. The magnetic propagation layer further comprises a central region in which the magnetic buses converge and are joined together. In another aspect, a method includes providing the magnetic device and generating the stream of domain walls propagating along the output magnetic bus.