Magnetic vortex dynamics in lithographically prepared nanodots is currently a subject of intensive research, particularly after recent demonstration that the vortex polarity can be controlled by in-plane magnetic field. This has stimulated the proposals of non-volatile vortex magnetic random access memories. In this work, we demonstrate that triangular nanodots offer a real alternative where vortex chirality, in addition to polarity, can be controlled. In the static regime, we show that vortex chirality can be tailored by applying in-plane magnetic field, which is experimentally imaged by means of Variable-Field Magnetic Force Microscopy. In addition, the polarity can be also controlled by applying a suitable out-of-plane magnetic field component. The experiment and simulations show that to control the vortex polarity, the out-of-plane field component, in this particular case, should be higher than the in-plane nucleation field. Micromagnetic simulations in the dynamical regime show that the magnetic vortex polarity can be changed with short-duration magnetic field pulses, while longer pulses change the vortex chirality.
Magnetoelectric domains and their switching mechanism in a Y-type hexaferrite
利用共振X射线显微衍射技术，我们对Y型六角铁氧体Ba $_{0.5}$ Sr $_{1.5}$ Mg $_2$ Fe $_{12}$ O $_{22}$的磁化强度和磁极性畴进行了成像。我们表明，磁极性域结构可以控制的磁场和电场，这些领域的完全反转可以简单地通过在没有一个电场偏置的情况下施加的磁场的逆转。此外，我们表明，在不同的X射线偏振通道测量的衍射强度不能再现的极性磁结构，被称为2扇横锥（TC）模型的公认的模型。我们提出了一个修改这个模型，实现了良好的定量协议与我们所有的数据。我们发现，TC模型的偏差是大的，可能是由于内部的磁手征，最有可能继承自父螺旋（非极性）相。
Neutron diffraction in MnSb2O6: Magnetic and structural domains in a helicoidal polar magnet with coupled chiralities
MnSb $_{2}$ O $_{6}$基于结构手性$P$ 321空间群#150，其中Mn $^{2+}$磁矩（$S=5/2$，$L\approx 0$）在$T_\mathrm{N}=12$ K下反铁磁性有序。与相关的铁基硅酸镧镓矿（Ba $_3$ NbFe $_3$ Si $_2$ O $_{14}$）不同，其中低温磁性基于以时间均匀赝标“磁”手性为特征的适当螺旋，MnSb $_{2}$ O $_{6}$中的Mn $^{2+}$离子在低温下具有摆线结构，而不是由时间均匀矢量“磁”极性描述。发现了一种倾斜的摆线结构[M. Kinoshita等人，Phys. Rev. Lett. 117，047201（2016）]以促进在施加的磁场下的铁电切换。在这项工作中，我们应用极化和非极化中子衍射分析的磁性和核结构的MnSb $_{2}$ O $_{6}$的目的是了解这种磁电耦合。我们没有发现任何证据的螺旋磁结构的自旋包络轴之一倾斜远离摆线$c$轴。然而，在施加磁场$\parallel$ $\vec{c}$时，自旋旋转平面可以倾斜，从而产生摆线-螺旋混合物，对于大于$\approx$ 2 T的磁场，该摆线-螺旋混合物朝向扭曲的螺旋（零摆线分量）演变。我们提出了一种机制，以前报道的铁电开关的基础上耦合的结构和磁性的手性只需要一个结构手性域的不平衡。
