Magnetic solitons are twisted spin configurations, which are characterized by a topological integer (textit{Q}) and helicity ($gamma$). Due to their quasi-particle properties, relatively smaller size, and the potential to set themselves into motion with smaller critical current densities than domain walls, they hold promising aspects as bits of information in future magnetic logic and memory devices. System having Dzyaloshinskii-Moriya Interaction (DMI) prefers a particular rotational sense, which determines a single value of Q and $gamma$. However, the case of frustrated ferromagnet is of particular interest since solitons with different $Q$ and $gamma$ can be stabilized. Recently, higher order skyrmion($Q>2$) and coexistence of skyrmion and antiskyrmion in frustrated ferromagnets has been predicted using $J_1$--$J_2$--$J_3$ classical Heisenberg model. cite{zxcv} In this work, we modelled a synthetic antiferromagnet (SAF) system to co-exist both skyrmion and antiskyrmion, but without considering frustrated exchange interaction. The bottom layer of the SAF has isotropic DMI and the top layer has anisotropic DMI. The presence of antiskyrmion and skyrmion in the two different layers may induce magnetic frustration in the SAF. Here we have varied the strength of Ruderman--Kittel--Kasuya--Yosida (RKKY) coupling as a perturbation and observed 6 novel elliptical skyrmionic states. We have observed that skyrmionic states have a 3 fold degeneracy and another two fold degeneracy. We also report a novel elliptical Q = 0 state.
تحميل البحث