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Skyrmions in thin films are spin textures across which the magnetization follows a cycloid with a unique sense of rotation, known as chirality. These specific magnetic patterns can be stabilized in various kinds of materials, and particularly in ultrathin trilayers with no inversion symmetry (e.g. heavy metal/ferromagnet/oxide) exhibiting simultaneously an interfacial interaction called Dzyaloshinskii-Moriya (DMI) and a strong perpendicular magnetic anisotropy (PMA). Since they are ideally topological solitons, skyrmions are currently attracting considerable interest both for the underlying physics and for their applicative potential. Their ability to be set in motion by electrical current opens the way to imagine them as dense storage data bits or magnetic logic operations. Furthermore, the possibility to tune magnetic interfacial properties by a gate voltage enables low power control of spintronic devices and provides a versatile, local and dynamic degree of freedom that can be implemented in innovative designs.

In this context, in collaboration with Institut Néel, we have recently shown that a gate voltage can not only switch skyrmions on and off but also tune the interface properties (PMA and DMI). The new mechanism leading to DMI revealed by our experiments allows expecting a control of DMI sign, which would lead to an inversion of the skyrmion’s chirality.

In this internship, we target to study by micromagnetic simulations the possibility to change DMI sign and to demonstrate voltage controlled skyrmion chirality switch. This breakthrough would open new possibilities for skyrmion manipulation, as a change of chirality would invert the direction of current-induced motion. It will also open new and rich physics on the dynamical control of the topology of these solitons.

• Keywords : Mathematics - Numerical analysis - Simulation, spintronics, IRIG, SPINTEC
• Laboratory : IRIG / SPINTEC
• CEA code : 191022-9
• Contact : liliana.buda@cea.fr