Coexistence of superconductivity and antiferromagentic order in Er 2 O 2 Bi with anti-ThCr 2 Si 2 structure

We investigated the coexistence of superconductivity and antiferromagnetic order in the compound Er 2 O 2 Bi with anti-ThCr 2 Si 2 -type structure through resistivity, magnetization, specific heat measurements and first-principle calculations. The superconducting transition temperature T c of 1.23 K and antiferromagnetic transition temperature T N of 3 K are observed in the sample with the best nominal composition. The superconducting upper critical field H c2 (0) and electron-phonon coupling constant λ e − ph in Er 2 O 2 Bi are similar to those in the previously reported non-magnetic superconductor Y 2 O 2 Bi with the same structure, indicating that the superconductivity in Er 2 O 2 Bi may have the same origin as in Y 2 O 2 Bi. The first-principle calculations of Er 2 O 2 Bi show that the Fermi surface is mainly composed of the Bi 6 p orbitals both in the paramagnetic and antiferromagnetic state, implying minor effect of the 4 f electrons on the Fermi surface. Besides, upon increasing the oxygen incorporation in Er 2 O x Bi, T c increases from 1 to 1.23 K and T N decreases slightly from 3 K to 2.96 K, revealing that superconductivity and antiferromagnetic order may compete with each other. The Hall effect measurements indicate that hole-type carrier density indeed increases with increasing oxygen content, which may account for the variations of T c and T N with different oxygen content.