Lee Oscar, Sahliger Jan, Aqeel Aisha, Khan Safe, Seki Shinichiro, Kurebayashi Hidekazu, Back Christian H
London Centre for Nanotechnology, University College London, United Kingdom.
Physik-Department, Technische Universität München, D-85748 Garching, Germany.
J Phys Condens Matter. 2021 Dec 13;34(9). doi: 10.1088/1361-648X/ac3e1c.
Recently, it has been shown that the chiral magnetic insulator CuOSeOhosts skyrmions in two separated pockets in temperature and magnetic field phase space. It has also been shown that the predominant stabilization mechanism for the low-temperature skyrmion (LTS) phase is via the crystalline anisotropy, opposed to temperature fluctuations that stabilize the well-established high-temperature skyrmion (HTS) phase. Here, we report on a detailed study of LTS generation by field cycling, probed by GHz spin dynamics in CuOSeO. LTSs are populated via a field cycling protocol with the static magnetic field applied parallel to the ⟨100⟩ crystalline direction of plate and cuboid-shaped bulk crystals. By analyzing temperature-dependent broadband spectroscopy data, clear evidence of LTS excitations with clockwise (CW), counterclockwise (CCW), and breathing mode (BR) character at temperatures below= 40 K are shown. We find that the mode intensities can be tuned with the number of field-cycles below the saturation field. By tracking the resonance frequencies, we are able to map out the field-cycle-generated LTS phase diagram, from which we conclude that the LTS phase is distinctly separated from the high-temperature counterpart. We also study the mode hybridization between the dark CW and the BR modes as a function of temperature. By using two CuOSeOcrystals with different shapes and therefore different demagnetization factors, together with numerical calculations, we unambiguously show that the magnetocrystalline anisotropy plays a central role for the mode hybridization.
最近的研究表明，手性磁绝缘体CuOSeO在温度和磁场相空间的两个分离区域中存在斯格明子。研究还表明，低温斯格明子（LTS）相的主要稳定机制是通过晶体各向异性，这与稳定已确立的高温斯格明子（HTS）相的温度涨落相反。在此，我们报告了一项关于通过场循环产生LTS的详细研究，该研究通过CuOSeO中的GHz自旋动力学进行探测。LTS通过场循环协议产生，其中静态磁场平行于板状和长方体状块状晶体的⟨100⟩晶体方向施加。通过分析温度相关的宽带光谱数据，在温度低于40 K时，清晰地显示出具有顺时针（CW）、逆时针（CCW）和呼吸模式（BR）特征的LTS激发的证据。我们发现，在低于饱和场的情况下，模式强度可以通过场循环次数进行调节。通过跟踪共振频率，我们能够绘制出场循环产生的LTS相图，从中我们得出结论，LTS相与高温对应相明显分离。我们还研究了暗CW模式和BR模式之间的模式杂化作为温度的函数。通过使用具有不同形状因而具有不同退磁因子的两块CuOSeO晶体，结合数值计算，我们明确表明磁晶各向异性在模式杂化中起核心作用。
