A skyrmion state in a non-centrosymmetric helimagnet displays topologically protected spin textures with profound technological implications for high density information storage, ultrafast spintronics, and effective microwave devices. Usually, its equilibrium state in a bulk helimagnet occurs only over a very restricted magnetic-field--temperature phase space and often in the low temperature region near the magnetic transition temperature Tc. We have expanded and enhanced the skyrmion phase region from the small range of 55-58.5 K to 5-300 K in single-crystalline Cu2OSeO3 by pressures up to 42.1 GPa through a series of phase transitions from the cubic P2(_1)3, through orthorhombic P2(_1)2(_1)2(_1) and monoclinic P2(_1), and finally to the triclinic P1 phase, using our newly developed ultrasensitive high-pressure magnetization technique. The results are in agreement with our Ginzburg-Landau free energy analyses, showing that pressures tend to stabilize the skyrmion states and at higher temperatures. The observations also indicate that the skyrmion state can be achieved at higher temperatures in various crystal symmetries, suggesting the insensitivity of skyrmions to the underlying crystal lattices and thus the possible more ubiquitous presence of skyrmions in helimagnets.
We report small angle X-ray scattering (SAXS) measurements of the skyrmion lattice in two 200~nm thick Cu$_2$OSeO$_3$ lamellae aligned with the applied magnetic field parallel to the out of plane [110] or [100] crystallographic directions. Our measurements show that the equilibrium skyrmion phase in both samples is expanded significantly compared to bulk crystals, existing between approximately 30 and 50~K over a wide region of magnetic field. This skyrmion state is elliptically distorted at low fields for the [110] sample, and symmetric for the [100] sample, possibly due to crystalline anisot…
Theoretical study on stabilization and destabilization of magnetic skyrmions by uniaxial-strain-induced anisotropic Dzyaloshinskii--Moriya interactions
Onset of a skyrmion phase by chemical substitution in MnGe chiral magnet
用中子小角散射方法研究了含$x$（$0 \leq x \leq 0.3$）的Mn $_{1-x}$ Fe $_{x}$ Ge合金的磁相图的演化。我们毫不含糊地观察到的skyrmion晶格（或A-相）在散装MnGe和其发病下一个小的Mn/Fe替代的情况下。在那里，A相被赋予特殊的skyrmion密度，并且在非常大的温度区域和与Fe浓度成比例的场范围内稳定。我们的研究结果强调了通过化学掺杂来微调Skyrmion晶格特性的可能性。
Néel-type skyrmion lattice in tetragonal polar magnet VOSe$_2$O$_5$
在四极磁体VOSe $_2$ O $_5$中发现了三角形Skyrmion晶格的形成。通过对单晶的磁化强度和小角中子散射的测量，我们确定了零场时的摆线自旋态和极轴方向上的磁场下的Néel型skyrmion晶格相。邻近这一阶段，另一个磁相的无公度自旋纹理被确定在较低的温度下，暂时分配到一个正方形skyrmion晶格相。这些发现揭示了块体材料中Néel型skyrmions的多功能特性，并为探索极性磁体中拓扑自旋纹理的物理学提供了一个独特的机会。
Cu2OSeO3 is known as a unique example of insulating multiferroic compounds with skyrmion spin texture, which is characterized by the chiral cubic crystal structure at ambient pressure. Recently, it has been reported that this compound shows pressure-induced structural transition with large enhancement of magnetic ordering temperature Tc. In the present study, we have investigated the detailed crystal structure in the high pressure phase, by combining the synchrotron X-ray diffraction experiment with the diamond anvil cell and the analysis based on the genetic algorithm. Our results suggest tha…
Proximity-Induced Skyrmion Stabilization at the Cu2OSeO3/Bi2Se3 Interface
Technical University of Munich（慕尼黑工业大学）；Munich Center for Quantum Science and Technology (MCQST)（慕尼黑量子科学与技术中心）；Center for Quantum Engineering (ZQE)（量子工程中心）；Helmholtz-Zentrum Berlin für Materialien und Energie（柏林亥姆霍兹材料能源研究中心）；University of Regensburg（雷根斯堡大学）；Institute for Experimental and Applied Physics, University of Regensburg（雷根斯堡大学实验与应用物理研究所）；University of Augsburg（奥格斯堡大学）；Institute of Physics, University of Augsburg（奥格斯堡大学物理研究所）
