Centrosymmetric Lattice with a Frustrated Triangular Lanthanide Nets: GdAuAl₄Ge₂and TbAuAl₄Ge₂

Similar to the centrosymmetric skyrmion lattice magnet Gd₂PdSi₃[1], the compounds LnAuAl4Ge2 (Ln = lanthanide) feature equilateral triangles of Ln ions within well separated planes [2]. This suggests that nontrivial magnetic states might also emerge in this family of materials. Here we focus on the Ln=Gd and Tb examples, where magnetization, heat capacity, and electrical transport measurements reveal complex magnetic ordering at low temperatures. In particular, the Gd compound shows three distinct transitions at T_1,Gd = 17.8 K, T_2,Gd = 15.6 K, and T_3,Gd = 13.8 K, and Tb compound shows two distinct transitions at T_1,Tb = 13.5 K, T_2,Tb = 9.7 K. This multiplicity of the ordered states reveals the presence of competing magnetic order parameters. Evidence for magnetic frustration is also seen in the form of strong magnetic fluctuations at temperatures well above the ordering temperatures. Finally, complex temperature-magnetic field phase diagrams are observed, with similarities to other metallic skyrmion host materials. We will present detailed electronic/magnetic phase diagrams for these compounds, compare them to other centrosymmetric skyrmion lattice compounds, and discuss prospects for uncovering similar behavior in the family of materials.