Superconducting Nd_1-EuNiO₂ thin films using in situ synthesis

We report on superconductivity in Nd_1-EuNiO₂ using Eu as a 4f dopant of the parent NdNiO₂ infinite-layer compound. We use an all-in situ molecular beam epitaxy reduction process to achieve the superconducting phase, providing an alternate method to the ex situ CaH₂ reduction process to induce superconductivity in the infinite-layer nickelates. The Nd_1-EuNiO₂ samples exhibit a step-terrace structure on their surfaces, have a T_c onset of 21 K at x = 0.25, and have a large upper critical field that may be related to Eu 4f doping.