Magnetic neutron diffraction in the novel triangular lattice antiferromagnet ErTa7O19

Rare-earth (RE) based geometrically frustrated magnets represent a promising avenue in the search of enigmatic quantum spin liquids (QSLs). Our previous study published in Nature Materials has identified a novel family of RE heptatantalates RETa7O19, where in the Nd case strong Ising anisotropy on the triangular lattice leads to a QSL state. As the nature of the RE has a strong influence on the magnetic anisotropy, which primarily determines the ground state on frustrated lattices, we hereby propose to study ErTa7O19 with the same crystal structure but twice as strong magnetic interactions and apparently XY magnetic anisotropy, according to our bulk magnetic measurements. Neither these nor specific-heat measurements show any signs of magnetic ordering down to 2 K. We propose a neutron diffraction study below 1 K to address the nature of the ground state in this compound.

基于稀土（Rare-earth, RE）的几何阻挫磁体，是探寻神秘量子自旋液体（quantum spin liquids, QSLs）的极具潜力的研究方向。我们此前发表于《自然·材料》的研究工作，已鉴定出一类新型稀土七钽酸盐RETa7O19家族材料，其中钕基（Nd）体系的三角晶格上存在强伊辛各向异性，进而呈现量子自旋液体态。由于稀土元素种类对磁各向异性具有显著调控作用，而磁各向异性是决定阻挫晶格基态性质的核心因素，结合前期块体磁性表征结果，我们提出对具有相同晶体结构的ErTa7O19开展研究：该体系的磁相互作用强度为前述Nd基体系的两倍，且表现出明显的XY型磁各向异性。无论是块体磁性测量还是比热测量，均未在低至2K的温区内观测到磁有序的相关迹象。因此我们计划开展低于1K的中子衍射实验，以阐明该化合物的基态本质。