Magnetic Racetrack Memory Domain Wall Energy Modulation
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Solution Overview
Problem
Existing magnetic racetrack memory devices face challenges with domain wall pinning and movement due to uniform energy profiles, leading to instability and inefficiency in data storage and retrieval, as domain walls can become stuck between pinning sites or overshoot their targets.
Innovation Solution
Incorporating undulating or modulated domain wall energy profiles along the racetrack with pinning sites, where energy minima are separated by energy barriers, allowing domain walls to move reliably and efficiently between stable positions using current pulses, and adjusting the racetrack shape and material properties to enhance pinning and reduce energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a uniform energy profile is used along the racetrack, then the structure is simple and easy to manufacture, but domain walls become unstable and can become stuck between pinning sites or overshoot their targets
Solution Approach 1:
The patent applies local quality by creating non-uniform energy profiles along the racetrack with specific pinning sites at locations corresponding to notches or variations in track geometry. These localized energy minima provide stable positions for domain walls, while the regions between pinning sites have higher energy, preventing domain walls from becoming stuck in unwanted positions. This local modification of energy landscape maintains manufacturing simplicity while dramatically improving domain wall stability and positioning reliability.
2Reliability
If longer current pulses are used to move domain walls, then domain walls can reliably reach their targets, but energy consumption increases and storage density decreases
Solution Approach 1:
The patent employs periodic action through the use of alternating current pulses to move domain walls between pinning sites. The current pulses are applied in a periodic manner, with each pulse duration optimized to move the domain wall a specific distance to the next stable position. This periodic driving mechanism allows reliable domain wall transport with minimized energy consumption, as each pulse is precisely timed and sized to achieve the desired displacement without excessive energy input.
Solution Approach 2:
The patent utilizes parameter changes by optimizing the duration, amplitude, and frequency of current pulses based on the specific racetrack geometry and domain wall properties. By carefully controlling these parameters, the system achieves reliable domain wall movement with minimal energy consumption. The pulse parameters are adjusted according to the distance between pinning sites and the energy barriers involved, enabling efficient data storage and retrieval operations.
3Device complexity
If domain walls are allowed to move freely without pinning sites, then the system is simpler, but domain walls cannot maintain stable positions for data storage
Solution Approach 1:
The patent implements local quality by introducing pinning sites at specific locations along the racetrack where the energy profile has local minima. These pinning sites, created through notches or geometric variations in the track, provide stable positions for domain walls to reside. The regions between pinning sites have higher energy, creating natural barriers that prevent domain walls from moving to unstable positions. This localized modification of the energy landscape enables reliable data storage while maintaining relatively simple device architecture.
4Ease of manufacture
If the racetrack has a uniform cross-section, then manufacturing is easier, but domain wall energy profile cannot be modulated to create stable pinning positions
Solution Approach 1:
The patent applies local quality by introducing localized geometric variations (notches) at specific positions along the racetrack to create pinning sites. These notches are precisely positioned to create energy minima that correspond to desired data storage locations. The majority of the racetrack maintains a uniform cross-section for ease of manufacture, while the pinning sites are precisely engineered at critical locations to provide the necessary energy modulation for stable domain wall positioning.
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 ensures domain walls consistently rest at stable positions, reduces the sensitivity to current pulse length, and enhances storage density by allowing for shorter pulse lengths and reduced energy consumption, improving the reliability and efficiency of data movement and storage.
Implementation Method 1
When this spin polarized current passes through into the next domain across the intervening domain wall, it develops a spin torque. This spin torque moves the domain wall.
Implementation Method 2
As the current passes through a domain, it becomes 'spin polarized'.
Implementation Method 3
DWs positioned in one of these segments at the end of a current pulse are relatively unstable and move towards a pinning site (a stable position) once the current is turned off, so as to minimize their energy.
Data Source
Figure 1A~1B
Figure 2A~2C
Figure 3A~3C
AI summary
A racetrack memory device facilitates the manipulation of a series of domain walls along the racetrack. The racetrack is designed so that the domain wall energy increases and decreases in a continuous fashion between adjacent pinning sites, so that a domain wall does not become stuck between them. The variation in the domain wall energy along the racetrack can be provided by continuous variations of the racetrack's width (while maintaining constant thickness) and/or cross-sectional area (in which the racetrack dimensions are varied in both directions perpendicular to the length of the racetrack). Alternatively, this variation in domain wall energy may be provided by varying the magnetic properties of the racetrack along the racetrack while otherwise keeping the shape and size of the racetrack unchanged. In addition, variations of the racetrack's composition and/or shape can be used.