salle 22-32-201
Hélène BEA – SPINTEC, (Univ. Grenoble Alpes/CNRS/CEA)
Abstract
Magnetic skyrmions are chiral spin textures that gathered a lot of attention due to their topological properties, their nanometer size and the possibility to efficiently move them with currents. In our era of information, their use as data bits for ultrafast and power-efficient devices has opened many possibilities of applications in spintronics memories or logic, but also in non-conventionnal computing, such as probabilistic and ultralow power computing or neuromorphic computing.
The chiral exchange called Dzyaloshinskii-Moryia interaction (DMI) is a key parameter to stabilize these quasi-particles. In heavy metal/ferromagnet/oxide ultrathin trilayers, DMI has an interfacial origin, similarly to surface magnetic anisotropy, and it is thus very sensitive to interface quality and material thicknesses.
In this seminar, I will present some results about the stabilization and manipulation of magnetic skyrmions in heavy metal/ferromagnet/oxide trilayers. Skyrmion phases can be stabilized in perpendicularly magnetized samples, when domain wall energy is decreased due to the vicinity of a transition, either towards paramagnetic phase or towards in-plane anisotropy behaviour. By finely controlling material parameters, the sign of DMI may be inverted, which switches skyrmion chirality. As a results, for a given driving current in the plane of the layers, the gate voltage modifies skyrmion speed and trajectories.
The use of a gate voltage modifies not only anisotropy, magnetization and Curie temperature, but also Dzyaloshinskii-Moriya interaction. On the one hand, the variation of DMI amplitude induces a change in skyrmion stability, thus allowing to realize a (room temperature) skyrmion switch. On the other hand, the control of DMI sign by a gate voltage allows to locally and dynamically reverse skyrmion chirality and motion. Hence, this local, persistent and reversible control of skyrmion stability and chirality offers a new degree of freedom to individually manipulate skyrmions with low power.
