Magnetic structures of non-stoichiometric Ln₂₋ₓTi₆₋ₓBi₉ (Ln = Tb and Er) Shurikagome Metals

The kagome-lattice compound TbTi₃Bi₄ has attracted considerable attention due to its giant anomalous Hall effect coupled with field-induced magnetization plateaus. We have synthesized a related family of Ln₂₋ₓTi₆₋ₓBi₉ (Ln = Tb and Er) shurikagome metals that feature quasi-two-dimensional titanium networks interlaced with chains of rare-earth elements. Both compounds crystallize in a tetragonal structure with space group P4/nmm and exhibit a pronounced antiferromagnetic-like cusp in the magnetic susceptibility at 12.7 K for Tb₂₋ₓTi₆₋ₓBi₉ (with x≈0.35) and 2.3 K for Er₂₋ₓTi₆₋ₓBi₉ (with x≈0.59). Rietveld analysis of the neutron powder diffraction patterns reveals that while both compounds share the same magnetic propagation vector (0 0 1/2), they display distinct antiferromagnetic orders. In Tb₂₋ₓTi₆₋ₓBi₉, the magnetic moments in the collinear antiferromagnetic order are oriented along the [1-10] direction, with the ordered moments of 7.24 and 5.49 μB at the two Tb sites. By contrast, Er₂₋ₓTi₆₋ₓBi₉ exhibits antiferromagnetic order with the magnetic moments aligned along the c axis. The distinct magnetic structures in Tb₂₋ₓTi₆₋ₓBi₉ and Er₂₋ₓTi₆₋ₓBi₉ provide valuable insights into their macroscopic magnetic and other physical properties.