We report the synthesis of the entire LnAuAl4Ge2 (Ln = Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, and Tm) series and focus on the magnetic properties of GdAuAl4Ge2 and TbAuAl4Ge2. Temperature and magnetic field dependent magnetization, heat capacity, and electrical resistivity measurements reveal that both compounds exhibit several magnetically ordered states at low temperatures, with evidence for magnetic fluctuations extending into the paramagnetic temperature region. For magnetic fields applied in the ab-plane there are several ordered state regions that are associated with metamagnetic phase transitions, consistent with there being multiple nearly degenerate ground states. Despite Gd being an isotropic S-state ion and Tb having an anisotropic J-state, there are similarities in the phase diagrams for the two compounds, suggesting that factors such as the symmetry of the crystalline lattice, which features well separated triangular planes of lanthanide ions, or the Ruderman-Kittel-Kasuya-Yosida interaction as defined by the Fermi surface topography control the magnetism. We also point out similarities to other centrosymmetric compounds that host skyrmion lattices such as Gd2PdSi3, and propose that the LnAuAl4Ge2 family of compounds are of interest as reservoirs for complex magnetism and electronic behaviors such as the topological Hall effect.
@article{arxiv.2205.14063,
title = {Magnetic Ordering in GdAuAl$_4$Ge$_2$ and TbAuAl$_4$Ge$_2$: layered compounds with triangular lanthanide nets},
author = {Keke Feng and Ian Andreas Leahy and Olatunde Oladehin and Kaya Wei and Minhyea Lee and Ryan Baumbach},
journal= {arXiv preprint arXiv:2205.14063},
year = {2022}
}