Doping Effects on the Electronic Structure of an Anisotropic Kondo Semiconductor CeOs2Al10: An Optical Study with Re and Ir Substitution

An anisotropic Kondo semiconductor CeOs2Al10 exhibits an unusual antiferromagnetic order at rather high transition temperature T0 of 28.5 K. Two possible origins of the magnetic order have been proposed so far, one is the Kondo coupling of the hybridization between the conduction (c) and the 4f states and the other is the charge-density wave/charge ordering along the orthorhombic b-axis. To clarify the origin of the magnetic order, we have investigated the electronic structure of hole- and electron-doped CeOs2Al10 [Ce(Os1−yRey)2Al10 and Ce(Os1−xIrx)2Al10, respectively] by using optical conductivity spectra along the b-axis. The intensity of the c–f hybridization gap at ħω ∼ 50 meV continuously decreases from y = 0.10 to x = 0.12 via x = y = 0. On the other hand, the intensity of the charge excitation observed at ħω ∼ 20 meV has the maximum at x = y = 0 as similar with the doping dependence of T0. The fact that the charge excitation is strongly related to the magnetic order strengthens the possibility of t...