254 research outputs found
Advances in the Physics of Magnetic Skyrmions and Perspective for Technology
Magnetic skyrmions are small swirling topological defects in the
magnetization texture stabilized by the protection due to their topology. In
most cases they are induced by chiral interactions between atomic spins
existing in non-centrosymmetric magnetic compounds or in thin films in which
inversion symmetry is broken by the presence of an interface. The skyrmions can
be extremely small with diameters in the nanometer range and, importantly, they
behave as particles that can be moved, created or annihilated, making them
suitable for abacus-type applications in information storage, logic or
neuro-inspired technologies. Up to the last years skyrmions were observed only
at low temperature (and in most cases under large applied fields) but important
efforts of research has been recently devoted to find thin film and
multilayered structures in which skyrmions are stabilized above room
temperature and manipulated by current. This article focuses on these recent
advances on the route to devices prototypes.Comment: Published online 13 June 2017 : 17 pages, 8 figures and 2 boxe
Electrical signature of individual magnetic skyrmions in multilayered systems
Magnetic skyrmions are topologically protected whirling spin textures that
can be stabilized in magnetic materials in which a chiral interaction is
present. Their limited size together with their robustness against the external
perturbations promote them as the ultimate magnetic storage bit in a novel
generation of memory and logic devices. Despite many examples of the signature
of magnetic skyrmions in the electrical signal, only low temperature
measurements, mainly in magnetic materials with B20 crystal structure, have
demonstrated the skyrmions contribution to the electrical transport properties.
Using the combination of Magnetic Force Microscopy (MFM) and Hall resistivity
measurements, we demonstrate the electrical detection of sub-100 nm skyrmions
in multilayered thin film at room temperature (RT). We furthermore analyse the
room temperature Hall signal of a single skyrmion which contribution is mainly
dominated by anomalous Hall effect.Comment: 13 pages, 4 figure
Resonant translational, breathing and twisting modes of pinned transverse magnetic domain walls
We study translational, breathing and twisting resonant modes of transverse
magnetic domain walls pinned at notches in ferromagnetic nanostrips. We
demonstrate that a mode's sensitivity to notches depends strongly on the
characteristics of that particular resonance. For example, the frequencies of
modes involving lateral motion of the wall are the ones which are most
sensitive to changes in the notch intrusion depth (especially at the narrower,
more strongly confined end of the domain wall). In contrast, the breathing
mode, whose dynamics are concentrated away from the notches is relatively
insensitive to changes in the notches' sizes. We also demonstrate a sharp drop
in the translational mode's frequency towards zero when approaching depinning
which is found, using a harmonic oscillator model, to be consistent with a
reduction in the local slope of the notch-induced confining potential at its
edge.Comment: 11 pages, 10 figures, additional data and analysi
Skyrmion Gas Manipulation for Probabilistic Computing
The topologically protected magnetic spin configurations known as skyrmions
offer promising applications due to their stability, mobility and localization.
In this work, we emphasize how to leverage the thermally driven dynamics of an
ensemble of such particles to perform computing tasks. We propose a device
employing a skyrmion gas to reshuffle a random signal into an uncorrelated copy
of itself. This is demonstrated by modelling the ensemble dynamics in a
collective coordinate approach where skyrmion-skyrmion and skyrmion-boundary
interactions are accounted for phenomenologically. Our numerical results are
used to develop a proof-of-concept for an energy efficient
() device with a low area imprint ().
Whereas its immediate application to stochastic computing circuit designs will
be made apparent, we argue that its basic functionality, reminiscent of an
integrate-and-fire neuron, qualifies it as a novel bio-inspired building block.Comment: 41 pages, 20 figure
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