CrPS₄中的各向异性磁子自旋输运
Anisotropic magnon spin transport in CrPS$_4$
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中文总结 AI 辅助
本研究以CrPS₄为对象，发现其磁子自旋输运存在显著各向异性，沿晶轴b方向的输运性能更优，揭示晶体各向异性可用于调控磁子自旋输运，为磁子器件研发提供新方向。
中文摘要 AI 辅助
晶体各向异性为实现固态系统中与方向相关的输运提供了有效途径。尽管其对电子输运的影响已得到充分证实，但各向异性在范德华磁体的磁子自旋输运中所起的作用在很大程度上尚未被探索。本研究采用非局域几何结构，利用单斜范德华反铁磁体CrPS₄，在电激发和热激发的磁子自旋输运中均观察到显著的各向异性。与沿晶轴a方向的输运相比，沿晶轴b方向输运时，电激发磁子的磁子自旋电导率至少大2.2倍，自旋扩散长度至少长2.7倍，其中λₘᵃ约为211nm，λₘᵇ不小于575nm。相比之下，在8T磁场、25K温度下，沿晶轴b方向与热激发磁子相关的非局域二次谐波电阻约为沿a方向的7倍。进一步研究表明，由于CrPS₄内部存在扩展的温度分布，无法从非局域二次谐波电阻中可靠提取磁子自旋扩散长度；同样，也无法仅通过热激发磁子自旋输运可靠估算自旋塞贝克系数的各向异性，因为该各向异性与CrPS₄的各向异性热导率相互交织。利用电激发磁子自旋输运，本研究证明本征晶体各向异性可作为调控磁子自旋输运的有效控制参数，为磁子器件工程开辟了新途径。
英文摘要
Crystal anisotropy provides a powerful route for realizing direction-dependent transport in solid-state systems. While its influence on electronic transport is well established, the role of anisotropy in magnon spin transport in van der Waals magnets is largely unexplored. Here, in a nonlocal geometry, utilizing the monoclinic van der Waals antiferromagnet CrPS$_4$, we observe pronounced anisotropy in both electrically and in thermally excited magnon spin transport. Electrically generated magnons exhibit a magnon spin conductivity at least 2.2 times larger and a spin diffusion length at least 2.7 times longer for transport along the crystallographic-b axis compared to the crystallographic-a axis, where $λ_m^{a} \sim$ 211 nm and $λ_m^{b} \geq$ 575 nm. In comparison, at 8T, we find the nonlocal second-harmonic resistance associated with thermally excited magnons to be $\sim$7 times larger along the crystallographic-b axis at 25K. We further show that a magnon spin diffusion length cannot be reliably extracted from the nonlocal second-harmonic resistance, owing to the extended temperature profile within CrPS$_4$. Likewise, we show that the anisotropy in the spin Seebeck coefficients cannot be reliably estimated from the thermally excited magnon spin transport alone, as it is intertwined with the anisotropic heat conductivity of CrPS$_4$. Utilizing the electrically generated magnon spin transport, we demonstrate that intrinsic crystalline anisotropy serves as an effective control parameter for tuning magnon spin transport, opening new avenues for magnonic device engineering.
