superconductors

Study of the magnetic effect and spin excitation in the Fe-based superconductors (FeSC) is crucial for understanding the origin of the superconductivity (SC) in the system. It’s believed that the anti-ferromagnetism (AF) order should be suppressed by particular dopants to induce SC in FeSC. With Ni and Co doping into Fe sites, the c type AFM ground state in BaFe₂As₂ is suppressed and altered into SC electronic phase. However, in Cr doped is of great interest to reveal the differences of the magnetic doping effect in BaFe₂As₂. Using scanning tunneling microscopy/spectroscopy, we studied the electronic properties in the Cr, Co and Ni doped BaFe₂As₂ crystals within AF, SC and AF/SC coexistence electronic phase, respectively. Superconducting phase separation and nanoscale inhomogeneity were found in Ba(Fe_0.92Ni_0.08)₂As₂ and Ba(Fe_0.96Co_0.04)₂As₂ superconductor crystals. Furthermore, electronic structures nearby defects of Cr, Ni and Co doped BaFe₂As₂, were compared systematically. Our results will shed light on the microscopic understanding of relation between the superconductivity and magnetism in the FeSC. This research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.