Long Hope A, Duong Daniel, Blawat Joanna, Morrison Gregory, Wu Yan, Cao Huibo, Pokhrel Nabaraj, Parker David S, Singleton John, Jin Rongying, Klepov Vladislav V
Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States.
SmartState Center for Experimental Nanoscale Physics, Department of Physics and Astronomy, University of South Carolina, Columbia, South Carolina 29208, United States.
J Am Chem Soc. 2025 May 7;147(18):15157-15169. doi: 10.1021/jacs.4c18438. Epub 2025 Apr 22.
HfCuSi-type pnictogen compounds have recently been shown to be a versatile platform for designing materials with topologically nontrivial band structures. However, these phases require strict control over the electron count to tune the Fermi level, which can only be achieved in compositions with AMPn and AMPn (A = lanthanides, M = transition metals, Pn = pnictogens P-Bi) charge distribution. While such lanthanide compounds have been thoroughly studied as candidate magnetic topological materials, their heavy element analogs with uranium and bismuth remain largely underexplored. In this report, we present the synthesis of UCuBi single crystals and study their magnetic properties. Detailed structural analysis revealed that flux-grown crystals always form as a site-deficient UCuBi composition, where varies between 0.20 and 0.64. Magnetic property measurements revealed a dependence of the magnetic coupling on the Cu site deficiency, linearly changing the Néel temperature from 51 K for UCuBi to 118 K for UCuBi. Moreover, higher Cu concentration promotes a metamagnetic transition in highly magnetically anisotropic UCuBi single crystals. We show that DFT calculations can successfully model site deficiency in the UCuSb and UCuBi systems. This work paves the way toward using the site deficiency to tune the Fermi level in more ubiquitous AMPn phases, which previously have not been considered topological candidate materials due to unfavorable electron count.
最近研究表明，HfCuSi型氮族化合物是设计具有非平凡拓扑能带结构材料的通用平台。然而，这些相需要严格控制电子数来调节费米能级，这只能在具有AMPn和AMPn（A = 镧系元素，M = 过渡金属，Pn = 氮族元素P - Bi）电荷分布的成分中实现。虽然这类镧系化合物作为候选磁性拓扑材料已得到充分研究，但其含铀和铋的重元素类似物仍基本未被充分探索。在本报告中，我们展示了UCuBi单晶的合成并研究了它们的磁性。详细的结构分析表明，助熔剂生长的晶体总是以缺位点的UCuBi成分形式形成，其中 在0.20至0.64之间变化。磁性测量表明，磁耦合依赖于Cu位点缺陷，将奈尔温度从UCuBi的51 K线性变化到UCuBi的118 K。此外，较高的Cu浓度促进了高度磁各向异性的UCuBi单晶中的变磁转变。我们表明，DFT计算可以成功地模拟UCuSb和UCuBi系统中的位点缺陷。这项工作为利用位点缺陷在更普遍的AMPn相中调节费米能级铺平了道路，这些相由于不利的电子数以前未被视为拓扑候选材料。
