Spin order and dynamics in the diamond-lattice Heisenberg antiferromagnets CuRh 2 O 4 and CoRh 2 O 4
Spin order and dynamics in the diamond-lattice Heisenberg antiferromagnets CuRh 2 O 4 and CoRh 2 O 4
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金刚石晶格海森堡反铁磁体 CuRh 2 O 4 和 CoRh 2 O 4 中的自旋顺序和动力学
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发表时间：
2017
期刊：
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通讯作者：
M. Mourigal
中科院分区：
文献类型：
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作者：
L. Ge;J. Flynn;J. Paddison;M. Stone;S. Calder;M. Subramanian;A. P. Ramirez;M. Mourigal
金刚石晶格上的反铁磁性绝缘体是承载奇异磁现象的候选材料，包括自旋-轨道纠缠、简并螺旋基态和拓扑顺磁。与其他三维磁性离子网络，如几何受挫的焦绿石晶格相比，对实际材料中的金刚石晶格磁性的研究还不够成熟。在这项工作中，我们用热磁和中子散射测量方法表征了A位尖晶石CoRh2O4(钴黄铁矿)和CuRh2O4(铜黄铁矿)的磁性质，并进行了群论分析、Rietveld精化、平均场理论和自旋波理论计算，对实验结果进行了分析。我们的研究表明，立方CoRh_2O_4是典型的S=3/2钻石晶格海森堡反铁磁体，其近邻交换J=0.63 meV，在25K以下为Neel有序基态。在四方扭曲的CuRh_2O_4中，近第三近邻自旋之间的竞争交换作用导致在24K时形成无公度的自旋螺旋，磁传播矢量k=(0，0，0.79)。观察到CuRh_2O_4中S=1/2自旋的有序矩的强烈还原，并被我们对交错磁化强度的1/S修正所捕获。我们的工作确定了CoRh2O4和CuRh2O4作为参考材料，以指导未来在钻石晶格反铁磁体中寻找奇异量子行为的工作。
Antiferromagnetic insulators on the diamond lattice are candidate materials to host exotic magnetic phenomena ranging from spin-orbital entanglement to degenerate spiral ground-states and topological paramagnetism. Compared to other three-dimensional networks of magnetic ions, such as the geometrically frustrated pyrochlore lattice, the investigation of diamond-lattice magnetism in real materials is less mature. In this work, we characterize the magnetic properties of model A-site spinels CoRh2O4 (cobalt rhodite) and CuRh2O4 (copper rhodite) by means of thermo-magnetic and neutron scattering measurements and perform group theory analysis, Rietveld refinement, mean-field theory, and spin wave theory calculations to analyze the experimental results. Our investigation reveals that cubic CoRh2O4 is a canonical S=3/2 diamond-lattice Heisenberg antiferromagnet with a nearest neighbor exchange J = 0.63 meV and a Neel ordered ground-state below a temperature of 25 K. In tetragonally distorted CuRh2O4, competiting exchange interactions between up to third nearest-neighbor spins lead to the development of an incommensurate spin helix at 24 K with a magnetic propagation vector k = (0,0,0.79). Strong reduction of the ordered moment is observed for the S=1/2 spins in CuRh2O4 and captured by our 1/S corrections to the staggered magnetization. Our work identifies CoRh2O4 and CuRh2O4 as reference materials to guide future work searching for exotic quantum behavior in diamond-lattice antiferromagnets.