Magnetoentropic mapping and computational modeling of cycloids and skyrmions in the lacunar spinels GaV4S8 and GaV4Se8
Magnetoentropic mapping and computational modeling of cycloids and skyrmions in the lacunar spinels GaV4S8 and GaV4Se8
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DOI：
10.1103/physrevmaterials.5.054410
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发表时间：
2021-05
影响因子：
3.4
通讯作者：
J. Zuo;D. Kitchaev;Emily C. Schueller;J. D. Bocarsly;R. Seshadri;A. Van der Ven;Stephen D. Wilson
中科院分区：
文献类型：
--
作者：
J. Zuo;D. Kitchaev;Emily C. Schueller;J. D. Bocarsly;R. Seshadri;A. Van der Ven;Stephen D. Wilson
本文报道了基于具有易轴各向异性和易平面各向异性的{\mathm{Gav}}_{4}{\mathm{S}}_{8}}和${\mathm{Gav}}_{4}{\mathm{se}}_{8}模型的磁熵映射用于快速识别单轴系统中的磁摆线和天米子相的可行性。我们表明，这些测量可以用一个简单的自旋哈密顿量的数值模型来解释，从而给出单相区和相界的明确赋值。在这两个空位尖晶石化学中，我们获得了测量的磁熵特征与建立在海森堡交换、单离子各向异性和各向异性Dzyaloshinskii-Moriya相互作用基础上的最小自旋哈密顿量之间的很好的一致性。特别是，我们确定了摆线相中的特征高熵行为，它是高温下天空微子形成的前兆，也是这种相变的一个容易测量的特征。我们的结果表明，数值模拟指导下的快速磁熵映射是理解Skyrmion主星固有的复杂磁相图的有效手段。一个值得注意的例外是在易平面系统中观察到了反常的低温高熵状态${\mathm{Gav}}_{4}{\mathm{se}}_{8}$，这在数值模型中没有被捕捉到。讨论了这种状态的可能起源。
We report the feasibility of using magnetoentropic mapping for the rapid identification of magnetic cycloid and skyrmion phases in uniaxial systems, based on the ${\mathrm{GaV}}_{4}{\mathrm{S}}_{8}$ and ${\mathrm{GaV}}_{4}{\mathrm{Se}}_{8}$ model skyrmion hosts with easy-axis and easy-plane anisotropies, respectively. We show that these measurements can be interpreted with the help of a simple numerical model for the spin Hamiltonian to yield unambiguous assignments for both single-phase regions and phase boundaries. In the two lacunar spinel chemistries, we obtain excellent agreement between the measured magnetoentropic features and a minimal spin Hamiltonian built on Heisenberg exchange, single-ion anisotropy, and anisotropic Dzyaloshinskii-Moriya interactions. In particular, we identify characteristic high-entropy behavior in the cycloid phase that serves as a precursor to the formation of skyrmions at elevated temperatures and is a readily measurable signature of this phase transition. Our results demonstrate that rapid magnetoentropic mapping guided by numerical modeling is an effective means of understanding the complex magnetic phase diagrams innate to skyrmion hosts. One notable exception is the observation of an anomalous, low-temperature high-entropy state in the easy-plane system ${\mathrm{GaV}}_{4}{\mathrm{Se}}_{8}$, which is not captured in the numerical model. Possible origins of this state are discussed.