The magnetic structure of a skyrmion is symmetrical around its core; arrows indicate the direction of spin. Credit: Ill./©: Benjamin Krüger
JGU and MIT joint teams have for the first time achieved targeted shifting of individual skyrmions at room temperature using electrical impulses. The idea is that electronic storage units (bits) will not be stored on rotating hard disks as is currently standard practice but on a nanowire in the form of magnetic vortex structures, ie skyrmions, using a process similar to that of a shift register. The magnetic skyrmion bits would be rapidly accessible, while storage density would be high and there would be improved energy efficiency.
Magnetic skyrmions are special spin configurations that can occur in materials especially in thin layer structures when the inversion symmetry is broken. This means a thin metal film with a non-symmetrical layer structure can be employed. In these materials spin configurations that behave rather like a hair whorl can form. It is as difficult to eradicate a skyrmion as it can be to smooth out whorl, thus skyrmions have enhanced stability.
An important characteristic of skyrmions is that they can exist in isolation in magnetic materials and generally do not tend to collide with the edge of a structure. This provides them with the unique ability to skirt any isolated defects or unevenness in the material with which other magnetic structures, such as domain walls, would collide. Skyrmions are therefore excellent candidates for use with magnetic shift registers, otherwise known as racetrack memory. Information could be encoded in the form of skyrmions and an electrical current could be employed to move them past fixed read/write heads. The process would be both rapid and completely independent of movable mechanical components and thus ideally suited for mobile applications.
It was demonstrated individual skyrmions can indeed be moved in a controlled manner along a magnetic wire, aka racetrack, by exposing them to brief electrical impulses at room temperature. In addition, new methods to describe their dynamics were developed and confirmed by experimentation. This work can thus be regarded as laying down the cornerstone for the future use of skyrmions in application-related systems. http://www.uni-mainz.de/presse/20165_ENG_HTML.php
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