Electronic structures of CeM₂Al₁₀ (M = Fe, Ru, and Os) studied by soft X-ray resonant and high-resolution photoemission spectroscopies

We have performed a photoemission spectroscopy (PES) study of CeM₂Al₁₀ ( M = Fe, Ru, and Os) to directly observe the electronic structure involved in the unusual magnetic ordering. Soft X-ray resonant (SXR) PES provides spectroscopic evidence of the hybridization between conduction and Ce 4 f electrons (c-f hybridization) and the order of the hybridization strength (Ru < Os < Fe). High-resolution (HR) PES of CeRu₂Al₁₀ and CeOs₂Al₁₀ , as compared with that of CeFe₂Al₁₀, identi fies two structures that can be ascribed to structures induced by the c-f hybridization and the antiferromagnetic ordering, respectively. Although the c-f hybridization-induced structure is a depletion of the spectral intensity (pseudogap) around the Fermi level (EF) with an energy scale of 20 -30meV, the structure related to the antiferromagnetic ordering is observed as a shoulder at approximately 10 -11 meV within the pseudogap. The energies of the shoulder structures of CeRu₂Al₁₀ and CeOs₂Al₁₀ are approximately half of the optical gap (20 meV), indicating that E_F is located at the midpoint of the gap.