Layered pnictide materials have provided a fruitful platform to study various emergent phenomena, including superconductivity, magnetism, charge density waves, etc. Here we report the observation of structural distortion and noncollinear magnetism in layered pnictide ${\mathrm{EuAg}}_4{\mathrm{As}}_2$ via transport, magnetization, single crystal x-ray, and neutron diffraction data. ${\mathrm{EuAg}}_4{\mathrm{As}}_2$ single crystal shows a structural distortion at 120 K, where two sets of superlattice peaks with the propagation vectors of $q_1=\pm$(0, 0.25, 0.5) and $q_2=\pm$(0.25, 0, 1) emerge. Between 9–15 K, the hexagonal ${\mathrm{Eu}}^{2+}$ sublattice enters an unpinned incommensurate magnetic state, with magnetic Bragg reflections pictured as circular sectors. Below 9 K, it orders in an incommensurate noncollinear antiferromagnetic state with a well-defined propagation wavevector of (0, 0.1, 0.12) and a very rare magnetic structure, which is helical along the $c$ axis and cycloidal along the $b$ axis with a moment of 6.4 ${\mu }_B/{\mathrm{Eu}}^{2+}$. Furthermore, rich magnetic phases under magnetic fields, large magnetoresistance, and strong coupling between charge carriers and magnetism in ${\mathrm{EuAg}}_4{\mathrm{As}}_2$ are revealed.

中文翻译：

---

EuAg4As2中的结构变形和非共线非共线磁性

层状磷化物材料为研究各种新兴现象提供了一个卓有成效的平台，包括超导性，磁性，电荷密度波等。在这里，我们报告观察到层状化物的结构变形和非共线磁性 ${\mathrm{Ag}}_4{如}_2$ 通过传输，磁化，单晶X射线和中子衍射数据。 ${\mathrm{Ag}}_4{如}_2$ 单晶在120 K处显示出结构畸变，其中两组超晶格峰的传播矢量为 $q_{\mathrm{1个}}=\pm$（0，0.25，0.5）和 $q_2=\pm$（0.25，0，1）出现。在9–15 K之间，六角形${\mathrm{欧洲联盟}}^{2+}$亚晶格进入不固定的不相称的磁性状态，磁性布拉格反射被描绘为圆形扇区。低于9 K时，它以不等的非共线反铁磁态排列，具有明确定义的（0，0.1，0.12）传播波矢量和非常稀有的磁结构，沿着$C$ 轴和摆线沿 $b$ 力矩为6.4的轴 ${\mu }_{乙}/{\mathrm{欧洲联盟}}^{2+}$。此外，磁场中的磁相丰富，磁阻大，并且电荷载流子与磁性之间的强耦合${\mathrm{Ag}}_4{如}_2$ 被揭示。