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TT: Fachverband Tiefe Temperaturen

TT 25: f-Electron Systems

TT 25.5: Talk

Tuesday, March 10, 2026, 10:30–10:45, HSZ/0101

Stoichiometry control of the magnetic structure and crystalline electric field effects in the Kondo lattice CeAlGe — •Soohyeon Shin and Yixi Su — Juelich Center for Neutron Sciense at MLZ, Lichtenbergstrasse 1, Garching 85748, Germany

CeAlGe crystallizes in the LaAlSi-type tetragonal structure, where spatial inversion symmetry is broken. This system is expected to host Weyl fermions near a Fermi surface that becomes more stable when time-reversal symmetry is broken. The magnetic ground state and associated topological properties of CeAlGe are known to depend sensitively on chemical stoichiometry. For instance, crystals grown by the flux method typically contain 5-15% excess Al on the Ge site and exhibit commensurate antiferromagnetic order below T=5.1 K. In contrast, crystals prepared by the floating-zone method under 30 bar of Ar gas yield stoichiometric compositions and display incommensurate order below T=4.4 K, where topological Hall effects are induced by external magnetic fields.

In this presentation, we report recent neutron-scattering experiments. Small-angle scattering reveals the emergence of additional incommensurate magnetic ordering associated with Al substitution. Furthermore, time-of-flight measurements suggest the presence of a magnetoelastic bound state between the first excited crystal-field level and an optical phonon mode near 17 meV. We will discuss the implications of this magnetoelastic bound state for the magnetic structures in CeAlGe.

Keywords: Kondo; magnetic skyrmion; stoichoimetry; crystalline electric field; magnetoelastic coupling