Structural control of d-f interaction in the CeFe1−xRuxAsO system system

The isovalent substitution effect of Ru in CeFe1−xRuxAsO (0 ≤ x ≤ 1) has been systematically studied by powder X-ray diffraction, electrical resistivity, magnetization, and specific heat measurements. The antiferromagnetic (AFM) ordering of both d and 4f electrons are suppressed upon Ru doping, followed by Pauli paramagnetism (d electrons) and local moment paramagnetism (4f electrons) with strong ferromagnetic fluctuation, respectively. Neither superconductivity above 2K nor pronounced Kondo screening are observed in the substitution phase diagram. Combined with published results of the cerium-based quaternary compounds CeMXO(M =Fe, Ru; X =P, As), our data suggest that the end member CeRuAsO is on the verge of becoming an FM Kondo lattice. Meanwhile, the ground state of 4f electrons in the quaternary CeMXO system should be determined by both the interlayer d-f Kondo coupling (JKondo) and the intralayer Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction (JRKKY ), which are both very sensitive to the change in crystal structure.