论文标题
与竞争交流互动的散装磁铁中跳跃的稳定性
Stability of Hopfions in Bulk Magnets with Competing Exchange Interactions
论文作者
论文摘要
磁跳是类似弦的三维拓扑孤子，其特征是HOPF不变。它们是三维磁准颗粒的基本原型，是Spintronics领域中新型设备概念的灵感。基于微磁模型并且在不考虑温度的情况下，已经在某些具有竞争交换相互作用的磁铁中预测了这种跳跃的存在。但是，到目前为止，散装磁铁中自由移动的跳跃的物理实现是难以捉摸的。在这里，我们考虑了一种有效的海森贝格模型，具有竞争交流相互作用，并通过在能量表面上找到一阶鞍点来代表衰减希望通过两个coupleped Bloch点的衰减的能量表面上的一阶鞍点，研究了与Hopf Number Number $ q_ \ text {h} = 1 $的小环形跳跃的稳定性。我们结合了测地上的弹性带方法和二聚体方法的改编实现，以解决鞍点附近反应路径的尖锐能谱。我们的分析表明，能量屏障可以达到很大的高度，并且在很大程度上取决于相对于晶格常数的跳跃大小。
Magnetic hopfions are string-like three-dimensional topological solitons, characterised by the Hopf invariant. They serve as a fundamental prototype for three-dimensional magnetic quasi-particles and are an inspiration for novel device concepts in the field of spintronics. Based on a micromagnetic model and without considering temperature, the existence of such hopfions has been predicted in certain magnets with competing exchange interactions. However, physical realisation of freely moving hopfions in bulk magnets have so far been elusive. Here, we consider an effective Heisenberg model with competing exchange interactions and study the stability of small toroidal hopfions with Hopf number $Q_\text{H}=1$ by finding first-order saddle points on the energy surface representing the transition state for the decay of hopfions via the formation of two coupled Bloch points. We combine the geodesic nudged elastic band method and an adapted implementation of the dimer method to resolve the sharp energy profile of the reaction path near the saddle point. Our analysis reveals that the energy barrier can reach substantial height and is largely determined by the size of the hopfion relative to the lattice constant.
