Superconducting Nd 1- x Eu x NiO 2 thin films using in situ synthesis.

We report on superconductivity in Nd 1- x Eu x NiO 2 using Eu as a 4f dopant of the parent NdNiO 2 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 CaH 2 reduction process to induce superconductivity in the infinite-layer nickelates. The Nd 1- x Eu x NiO 2 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.