物理学院“博约学术论坛”系列报告
第86期     (2016年第13期)

Title：Skyrmions and multi-sublattice helical states in a frustrated chiral magnet
报告人：袁怀洋 博士 (德国美茵茨大学物理系)
时   间：10月10日（周一）上午10：00
地   点：中心教学楼610
ABSTRACT
We investigate the existence and stability of skyrmions in a frustrated chiral ferromagnet by considering the competition between ferromagnetic (FM) nearest-neighbour (NN) interaction (J1) and antiferromagnetic (AFM) next-nearest-neighbour (NNN) interaction (J2). Contrary to the general wisdom that long-range ferromagnetic order is not energy preferable under frustration, the skyrmion lattice not only exists but is even stabile for a large field range when J2>J1 compared with frustration-free systems. We defend that the enlargement of stability window of skyrmions is a consequence of the reduced effective exchange interaction caused by the frustration. A multi-sublattice helical state is found below the skyrmion phase, which results from the competition between AFM coupling that favors a two-sublattice Neel state and the chiral interaction that prefers a helix. As a byproduct, the hysteresis loop of the frustrated chiral system shrinks as the magnetization goes to zero and then opens up again, known as wasp-waist hysteresis loop. The critical field that the separates the narrow and wide part of the wasp-waist loop depends exponentially on the strength of NNN coupling. By measuring the critical field, it is possible to determine the strength of NNN coupling.
Curriculum Vitae
 

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