Affecting the structure of skyrmions using ferromagnetic nanodisks with inhomogeneous properties: switching skyrmion helicity and polarity

Abstract

Topological stability of skyrmions is an important element for using these objects in new technologies such as skyrmionics, spintronics and so on. Indeed, this kind of stability keeps the skyrmion structure unbending, shielding the information that, by chance, it could carry. On the other hand, a controlled manipulation of the skyrmion configuration could be an extra ingredient for technological applications. It is not an easy task and particularly, the control of skyrmion polarity and chirality (for Block-type), and helicity (for Néel-type) may be important in this direction. Here, we have investigated the skyrmion oscillatory motion in a hybrid nanodisk by using atomistic spin dynamics simulations. If a skyrmion is put to oscillate in a disk formed by two different materials, having opposite Dzyaloshinskii-Moriya interactions ($D_{1}=-D_{2}$), then, its helicity experiences an inversion. Nonetheless, if the skyrmion oscillations occur in a homogeneous disk submitted to opposites magnetic fields in distinct regions (for instance, semi-disks $1$ and $2$), the skyrmion polarity and helicity suffer an inversion. Such skyrmionic-oscillators could provide a dynamical degree of freedom, yielding new functionalities to skyrmion-based logic devices.

Skyrmion transport and annihilation in funnel geometries

“…Material imperfections, such as vacancies, impurities, or grains with different anisotropy values can add an extra pinning effect [14,64] and also affect the annihilation process [65]. Moreover, regions in the sample with different DM values can change the skyrmion helicity and consequently modify the dynamics [66]. The implications of material imperfections on the skyrmion dynamics is a very important topic and further studies addressing these issues will be considered in future works.…”