Structural distortion and incommensurate noncollinear magnetism in EuAg4As2
Structural distortion and incommensurate noncollinear magnetism in EuAg4As2
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DOI：
10.1103/physrevmaterials.4.064419
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发表时间：
2018-09
期刊：
影响因子：
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通讯作者：
B. Shen;Chaowei Hu;H. Cao;X. Gui;E. Emmanouilidou;W. Xie;N. Ni
中科院分区：
文献类型：
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作者：
B. Shen;Chaowei Hu;H. Cao;X. Gui;E. Emmanouilidou;W. Xie;N. Ni
层状磷氮化合物材料为研究各种新兴现象提供了一个富有成效的平台，包括超导、磁性、电荷密度波等。在这里，我们通过输运、磁化、单晶X射线和中子衍射数据报告了层状磷氮化合物EuAg$_4$As$_2$中结构畸变和非共线磁性的观察。 EuAg$_4$As$_2$单晶在120 K时表现出结构畸变，出现两组传播矢量为$q_1=\pm$(0, 0.25, 0.5)和$q_2=\pm$(0.25, 0, 1)的超晶格峰。在 9 K 到 15 K 之间，六边形 Eu$^{2+}$ 子晶格进入非钉扎状态，磁布拉格反射被描绘为圆形扇区。低于 9 K，它处于不相称的非共线反铁磁状态，具有明确的传播波矢 (0, 0.1, 0.12)，其中磁结构沿 $c$ 轴呈螺旋状，沿 $b$ 轴呈摆线状，力矩为 6.4 $\mu_B$/Eu$^{2+}$。此外，EuAg$_4$As$_2$在磁场下具有丰富的磁相、大磁阻以及载流子与磁性之间的强耦合。
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 EuAg$_4$As$_2$ via transport, magnetization, single crystal X-ray and neutron diffraction data. EuAg$_4$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 K to 15 K, the hexagonal Eu$^{2+}$ sub-lattice enters an unpinned 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), where the magnetic structure is helical along the $c$ axis and cycloidal along the $b$ axis with a moment of 6.4 $\mu_B$/Eu$^{2+}$. Furthermore, rich magnetic phases under magnetic fields, large magnetoresistance, and strong coupling between charge carriers and magnetism in EuAg$_4$As$_2$ are revealed.