Electronic structure and magnetism in the layered triangular lattice compound CeAuAl4Ge2

Abstract

Results are reported for the f-electron intermetallic CeAuAl4Ge2, where the atomic arrangement of the cerium ions creates the conditions for possible geometric frustration. The magnetic susceptibility follows a Curie-Weiss temperature dependence at elevated temperatures, revealing that the cerium ions are trivalent. At lower temperatures the crystal electric field splits the Hund's rule multiplet, resulting in a weak low-temperature magnetic exchange interaction and ordering near TM≈1.4K. This occurs within a metallic Kondo lattice, where electrical resistivity and heat capacity measurements show that the Kondo-driven electronic correlations are negligible. Quantum oscillations are detected in ac-magnetic susceptibility measurements and uncover small charge carrier effective masses. Electronic structure calculations reveal that inclusion of an on-f-site Coulomb repulsion (Hubbard) U results in antiferromagnetic order and causes the f-electron bands to move away from the Fermi level, resulting in electronic behavior that is dominated by the s,p, and d bands, which are all characterized by light electron masses. Thus, CeAuAl4Ge2 may provide a starting point for investigating geometric magnetic frustration in a cerium lattice without strong Kondo hybridization, where calculations provide useful guidance.