Electric-Field-Induced Skyrmion Distortion and Giant Lattice Rotation in the Magnetoelectric Insulator Cu2OSeO3

Uniquely in Cu2OSeO3, the Skyrmions, which are topologically protected magnetic spin vortexlike objects, display a magnetoelectric coupling and can be manipulated by externally applied electric (E) fields. Here, we explore the E-field coupling to the magnetoelectric Skyrmion lattice phase, and study the response using neutron scattering. Giant E-field induced rotations of the Skyrmion lattice are achieved that span a range of similar to 25 degrees. Supporting calculations show that an E-field-induced Skyrmion distortion lies behind the lattice rotation. Overall, we present a new approach to Skyrmion control that makes no use of spin-transfer torques due to currents of either electrons or magnons.

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Arash Alahgholipour Omrani, Helmuth Berger, Ping Huang, Arnaud Magrez, Krunoslav Prsa, Henrik Moodysson Rønnow, Jonathan White, Ivica Zivkovic
American Physical Society, 2014
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https://infoscience.epfl.ch/record/202329?ln=fr

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Neutron scattering

Neutron scattering, the irregular dispersal of free neutrons by matter, can refer to either the naturally occurring physical process itself or to the man-made experimental techniques that use the natu

Skyrmion

Le skyrmion est une particule théorisée en 1962 par le physicien britannique Tony Skyrme et dont la découverte a été annoncée en 2009 par des physiciens de l'Université technique de Munich. Son a

Électricité

vignette|alt=Arcs électriques dans un ciel bleu allant des nuages au sol.|La foudre est l'un des phénomènes électriques les plus impressionnants qui existent. L’électricité est l'ensemble des phénomèn

Electric field control of the skyrmion lattice in Cu2OSeO3

Arash Alahgholipour Omrani, Helmuth Berger, Krunoslav Prsa, Henrik Moodysson Rønnow, Jonathan White, Ivica Zivkovic

Small-angle neutron scattering has been employed to study the influence of applied electric (E-) fields on the skyrmion lattice in the chiral lattice magnetoelectric Cu2OSeO3. Using an experimental geometry with the E-field parallel to the [111] axis, and the magnetic field parallel to the [1 (1) over bar0] axis, we demonstrate that the effect of applying an E-field is to controllably rotate the skyrmion lattice around the magnetic field axis. Our results are an important first demonstration for a microscopic coupling between applied E-fields and the skyrmions in an insulator, and show that the general emergent properties of skyrmions may be tailored according to the properties of the host system.

Institute of Physics2012

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Control of Topological Magnetic Textures by Magnetic and Electric Fields in Magnetoelectric Helimagnet Cu₂OSeO₃

Ping Huang

Magnetic skyrmions, topologically non-trivial chiral whirl-like spin configurations, have been under massive investigations in both fundamental and application aspects. In some special compounds, these quasi-particles can formtriangular skrymion lattice (SkL) exhibiting abundant unique properties. This thesis presents my comprehensive studies on the SkL in the magnetoelectric (ME) coupling helimagnet Cu2OSeO3. Starting from measurements on single crystal bulk Cu2OSeO3 samples, including dc magnetization, magnetoelectric susceptibility and neutron scattering, so as to get the general understanding of this system, the main work of this thesis focused on the investigation of quasi-two dimensional thin slab samples by the state-of-the-art Lorentz electron transmission electron microscopy (LTEM). Variousmagnetic textures including the spin helices and skyrmions were observed and analyzed. What separates the work presented here from literatures is the special emphasis on the dynamics of the SkL under various excitations in real space and real time, such as thermal fluctuation, magnetic field and electric field. Specifically, the magnetic field induced melting of the SkL in Cu2OSeO3 was, for the first time, observed and analyzed quantitatively. Two-step melting process was observed and demonstrated to follow the Kosterlitz-Thouless-Halperin-Nelson-Young (KTHNY) theory. The application of electric field can not only rotate the SkL, but also create skyrmions fromthe helical phase. My studies, especially those focused on the emergent properties induced by external fields, are intended to provide deeper insight into the fundamental knowledge of the SkL in Cu2OSeO3 and to promote the the development of skyrmion based spintronic applications.

EPFL2017

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Electric Field Effects in the Skyrmion Lattice Hosting Magnet Cu2OSeO3

Saumya Shivam

Magnetic skyrmions have garnered much attention in recent years because of their non trivial topology and potential to be used in next generation memory devices. They may exist individually or as a lattice of skyrmions(SkL). A number of investigations have been done on SkL in metallic samples, but recently a few magnetoelectric insulators have also begun to attract a lot of attention. The magnetoelectric nature of these materials presents a possibility to make prototype memory devices where skyrmions form a storage bit and can be controlled with only electric fields without the losses caused by Joule heating. We focus here on the material Cu2OSeO3, for which interesting electric field effects have been seen like the control of size of the region in the phase diagram where SkL is stable, creation of metastable skyrmions and the use of magnetolectric susceptibility to map the phase diagram. We use the magnetoelectric susceptibility to explore the above mentioned effects of electric fields, attempting to confirm previous reports of such effects using different techniques like neutron scattering and AC susceptibility. We also propose a new design to create metastable SkL state at low temperatures and confirm its existence using magnetoelectric susceptibility. We also attempt to measure the change in polarization between the SkL phase and the trivial phase on application of DC electric fields, which in principle could lead to electrical readout of skyrmions in a prototype skyrmion based memory device.

2018

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