arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2212.01320cond-mat.mes-hall
收藏

具有竞争交换作用的块体磁体中Hopfions的稳定性

Stability of Hopfions in Bulk Magnets with Competing Exchange Interactions

Moritz Sallermann, Hannes Jónsson, Stefan Blügel

摘要:

磁霍普夫子是一种具有霍普夫不变量的三维拓扑孤子。它们是三维磁性准粒子的基本原型,也是自旋电子学领域新器件概念的灵感来源。基于一个微磁模型,在不考虑温度的情况下,在某些具有竞争交换相互作用的磁体中,已经预测了这种hopfions的存在。然而,物理实现自由移动的hopfions在大块磁铁迄今为止一直难以捉摸。在这里,我们考虑一个有效的海森堡模型与竞争交换相互作用和研究的稳定性的小环形的Hopf数$Q_\text{H}=1$通过寻找一阶鞍点的能量表面上的代表过渡态的衰变通过形成两个耦合的布洛赫点。我们结合测地线轻推弹性带方法和二聚体方法的适应性实现解决鞍点附近的反应路径的尖锐的能量分布。我们的分析表明,能量势垒可以达到相当高的高度,在很大程度上是由相对于晶格常数的霍普夫子的大小。

英文摘要:

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.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑