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We used high-energy resolution angle-resolved photoemission spectroscopy to extract the momentum dependence of the superconducting gap of Ru-substituted Ba(Fe$_{0.75}$Ru$_{0.25}$)$_2$As$_2$ ($T_c = 15$ K). Despite a strong out-of-plane warping of the Fermi surface, the magnitude of the superconducting gap observed experimentally is nearly isotropic and independent of the out-of-plane momentum. More precisely, we respectively observed 5.7 meV and 4.5 meV superconducting gaps on the inner and outer $Gamma$-centered hole Fermi surface pockets, whereas a 4.8 meV gap is recorded on the M-centered electron Fermi surface pockets. Our results are consistent with the $J_1-J_2$ model with a dominant antiferromagnetic exchange interaction between the next-nearest Fe neighbors.
We have studied the anisotropy in the in-plane resistivity and the electronic structure of isovalent Ru-substituted BaFe$_2$As$_2$ in the antiferromagnetic-orthorhombic phase using well-annealed crystals. The anisotropy in the residual resistivity co
The Ru doping effect on the Dirac cone states is investigated in iron pnictide superconductors Ba(Fe$_{1-x}$Ru$_x$As)$_2$ using the transverse magnetoresistance (MR) measurements as a function of temperature. The linear development of MR against magn
We studied nearly optimally Ni-substituted BaFe$_{2-x}$Ni$_x$As$_2$ (BFNA) single crystals with $T_C approx 18.5$,K. In irreversible magnetization measurements, we determined the field dependence of the critical-current density and discuss the nature
We have employed the x-ray resonant magnetic scattering (XRMS) technique at the Ru $L_2$ edge of the Ba(Fe$_{1-x}$Ru$_x$)$_2$As$_2$ ($x = 0.205$) superconductor. We show that pronounced resonance enhancements at the Ru $L_2$ edge are observed at the
Single crystals of Ba(Fe$_{1-x}$Ru$_x$)$_2$As$_2$, $x<0.37$, have been grown and characterized by structural, magnetic and transport measurements. These measurements show that the structural/magnetic phase transition found in pure BaFe$_2$As$_2$ at 1