Local Structure Analysis of Heavy Fermion Ce2Pt6Ga15 with a Honeycomb Structure Using Extended X-Ray Absorption Fine Structure

Ce2Pt6Ga15 is a heavy fermion compound near the quantum critical point (QCP). Its crystal structure may exhibit magnetic frustration due to a honeycomb arrangement; however, stacking faults in the crystal hinder structural analysis. As a local structure probe, extended X-ray absorption fine structure (EXAFS) is less sensitive to stacking faults and is a powerful tool for crystal structure determination. We synthesized single-crystal Ce2Pt6Ga15, performed single-crystal and powder X-ray diffraction experiments, and conducted X-ray absorption spectroscopy (XAS) measurements. The composition of Ce2Pt6Ga15 deviates from stoichiometry, suggesting Ce and Ga enrichment or Pt site deficiencies. A comparison of X-ray absorption near-edge structure (XANES) at the Ce L3-edge with reference materials suggests that Ce valence is likely trivalent. To determine the exact structure, we simultaneously analyzed EXAFS spectra at the Ce L3-, Pt L3-, and Ga K-edges. The EXAFS spectra of Ce2Pt6Ga15 are inconsistent with the hexagonal Sc0.6Fe2Si4.9-type structure but are better explained by an orthorhombic structure with a honeycomb arrangement.