Closed-Loop Magnetic Domain Wall Counter With Gap-Bridged Spirals
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Solution Overview
Problem
Existing revolution counters using magnetic domain wall conductors in continuous spirals face issues with increasing defects, conductor length, and required chip surface area, limiting their effectiveness and cost-efficiency for counting more than 64 revolutions, and previous solutions for closed loops suffer from reduced magnetic windows and increased interference susceptibility.
Innovation Solution
A closed-loop revolution counter design with gaps between magnetic domain wall conductors, where the gap is bridged by a second conductor with a non-magnetic layer, allowing for domain wall movement without pinning, and enabling a larger magnetic window and reduced interference susceptibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the length of the continuous magnetic conductor is increased to count more revolutions, then the counting range increases, but the likelihood of defects increases disproportionately
Solution Approach 1:
The continuous magnetic conductor is divided into multiple separate closed-loop conductors instead of using one long continuous conductor. Each closed loop contains a specific number of windings (e.g., 5, 7, 9, 13), and the total counting range is achieved by combining multiple loops. This segmentation reduces the length of each individual conductor, thereby reducing the probability of defects in each loop while maintaining the overall counting capability through the combination of multiple loops.
2Quantity of substance
If the number of windings N is increased, then the counting range increases, but the chip surface area required increases increasingly
Solution Approach 1:
The spiral structure is segmented into multiple closed loops, each with a moderate number of windings. Instead of one large spiral requiring extensive chip area, multiple smaller closed loops are used. The closed-loop configuration allows for more compact arrangement compared to an open spiral, reducing the overall chip surface area required while achieving the same or greater counting range through the combination of multiple loops.
3Reliability
If closed loops are used to reduce conductor length, then yield improves, but the magnetic window decreases and interference susceptibility increases
Solution Approach 1:
Non-magnetic layers are introduced as intermediary materials at specific locations within the closed-loop magnetic conductor structure. These non-magnetic layers serve to shield or isolate magnetic domains, preventing unwanted magnetic interference and domain wall pinning effects that would otherwise reduce the magnetic window. The non-magnetic intermediaries maintain the benefits of closed-loop construction while mitigating the negative effects on magnetic performance and interference susceptibility.
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 solution provides a more reliable and cost-effective revolution counter with a wider magnetic window, reducing the risk of defects and interference, and allowing for efficient counting of a larger number of revolutions without increasing the sensor's surface area.
Implementation Method 1
magnetic domain walls moving in continuous magnetic regions that can be regarded as magnetic conductors
Implementation Method 2
The read-out principle uses magnetoresistive effects
Implementation Method 3
a stray field is generated therein and, in the movement direction downstream from the gap 201, results in nucleation of a domain wall DW in the subsequent domain conductor section
Data Source
AI summary
In a revolution counter using magnetic domain wall conductors which are wound each as a loop in a form of a spiral configured to be closed, in the connecting region the inner and outer loop section ends of the loop of a first magnetic domain wall conductor are combined and bridged by a second magnetic domain wall conductor which is connected to the magnetic domain wall conductor ends of the spiral with a respective gap therebetween, wherein the gap creates a local interruption of the domain wall conductor, and wherein the mean width of the gap is set to be smaller than the thickness of the domain wall conductors, and the adjoining domain conductor sections are encompassed by a non-magnetic layer in the gap region.