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Influence of electronic structure parameters on the electrical transport and magnetic properties of $Y_{2-x}Bi_xIr_2O_7$ pyrochlore iridates

We report the systematic study of structural, magnetic and electrical transport properties of $Y_{2-x}Bi_xIr_2O_7$ (x = 0.0, 0.1, 0.2, 0.3) pyrochlore iridates. The chemical doping enhances electrical conductivity and antiferromagnetic correlation substantially. The replacement of non-magnetic $Y^{3+}$ ion with non-magnetic $Bi^{3+}$ in $Y_2Ir_2O_7$ tends to reduce the octahedral distortion thus enhancing the antiferromagnetic correlation. Raman spectroscopy shows that the $Ir-O$ bond contract slightly and the $R-O'$ bond turn longer as disorder and phononic oscillation are reduced with $Bi$ doping, leading to wider $t_{2g}$ bands, which enhances the electrical conductivity. Additionally, the enhancement in electrical conductivity and antiferromagnetic correlation with $Bi^{3+}$ doping is attributed to the hybridization between the $Y^{3+}(4p)$/$Bi^{3+}(6s/6p)$ orbital with $Ir^{4+}(5d)$ orbital as a result of enhancement in $Ir-O-Ir$ bond angle and contraction in $Ir-O$ bond length.