Coexistence of high electrical conductivity and weak ferromagnetism in Cr doped Y_2Ir_2O_7 pyrochlore iridates

摘要

We report the structural, magnetic, and electrical transport properties ofY 2Ir2 - xCr xO 7 pyrochlore iridates. Chemical doping leads to the order of magnitude enhancement of electrical conductivity. The introduction ofCr3 + at theIr4 + site tends to distort theIr -O 6 octahedra and weakens antiferromagnetic correlation. The x-ray photoemission spectroscopy measurements suggest the coexistence ofIr4 + andIr5 + valence states in theY 2Ir2 - xCr xO 7 compounds. The concentration ofIr5 + is enhanced with Cr doping, leading to weak ferromagnetism and enhanced electrical conductivity. A cluster-glass-like transition is also observed at low temperatures with Cr doping, possibly due to competing ferromagnetic and antiferromagnetic interaction.