Geometrically enhanced closed-loop multi-turn sensor devices that enable reliable magnetic domain wall motion

Abstract

We experimentally realize a sophisticated structure geometry for reliable magnetic domain wall-based multiturn-counting sensor devices, which we term closed-loop devices that can sense millions of turns. The concept relies on the reliable propagation of domain walls through a cross-shaped intersection of magnetic conduits, to allow the intertwining of loops of the sensor device. As a key step to reach the necessary reliability of the operation, we develop a combination of tilted wires called the syphon structure at the entrances of the cross. We measure the control and reliability of the domain wall propagation individually for cross-shaped intersections, the syphon geometries and finally combinations of the two for various field configurations (strengths and angles). The various measured syphon geometries yield a dependence of the domain wall propagation on the shape that we explain by the effectively acting transverse and longitudinal external applied magnetic fields. The combination of both elements yields a behaviour that cannot be explained by a simple superposition of the individual different maximum field operation values. We identify as an additional process the nucleation of domain walls in the cross, which then allows us to fully gauge the operational parameters. Finally, we demonstrate that by tuning the central dimensions of the cross and choosing the optimum angle for the syphon structure reliable sensor operation is achieved, which paves the way for disruptive multi-turn sensor devices.

Wind driven semiconductor electricity generator with high direct current output based on a dynamic Schottky junction

“…As a proof of concept, using a special design with a polyimide insulating layer attached to the surface of a silicon rod, a portable turn counter has been obtained, whose mechanism is in contrast to the common magnetic turn-counting sensors. [42][43][44] The wind driven semiconductor electricity generator has also been used to drive a graphene photodetector, which exhibits responsivity of over 35.8 A W À1 . This demonstrates a potential method for direct power supply for driving widely distributed sensors in the age of the IoTs.…”

Stabilizing Zero-Field Skyrmions at Room-Temperature in Perpendicularly Magnetized Multilayers

“…Chiral magnets [1][2][3][4][5][6][7][8] have been investigated intensively in the last years due to their fascinating physical concepts and potential use in applications including sensors [9][10][11], logic [12][13][14], and magnetic memory devices [15,16]. Among different magnetic structures, domain walls [17], vortices [18], and skyrmions [19] have been investigated both theoretically and experimentally.…”

Strain-controlled Domain Wall injection into nanowires for sensor applications

“…This intense research has enabled the use of DWs in memory devices 3 and magnetic sensors 4 . For example, a DW can be used to carry information about the angular position of an object and to count the number of rotations performed in a nonvolatile way [5][6][7] . The interest of magnetic sensors based on DWs is in their stability, making their non-volatile positioning suitable to many applications.…”

“…At the same time, uncontrolled nucleation of domain walls at higher fields needs to be avoided, thus setting the maximum operation field value. Previous studies about DW sensors investigated the propagation and nucleation fields, and showed how they depend on material parameters and device geometry [7][8][9][10][11][12] . While the field operation window in idealized operation conditions is known, in real devices further factors play a role and have been previously neglected.…”