Absence of superconductivity in bulk Nd1−xSrxNiO2

Abstract

AbstractSuperconductivity at 9–15 K was recently discovered in Nd0.8Sr0.2NiO2 films. Since the Ni1+ ionic state in NdNiO2 may have the same 3d9 outer-shell electronic orbital as in cuprate superconductors, it is interesting to know whether superconductivity has a similar mechanism in these two systems. Here we synthesize bulk samples of Nd1−xSrxNiO2 (x = 0, 0.2, 0.4) with inhomogeneous Sr distribution and Ni deficiency. Resistivity measurements show insulating behavior without the presence of superconductivity, different to the previously reported films. Although applying pressure up to about 50.2 GPa significantly suppresses the insulating behavior, superconductivity remains absent. The magnetization behavior exhibits a Curie–Weiss law with a paramagnetic moment of about 2 μB/f.u. Since the lattice constants derived from our diffraction data are very close to the previously reported superconducting Nd0.8Sr0.2NiO2 films, we suggest that superconductivity in that system may have arisen from interface or stress-related effects, or nickel deficiency in our bulk samples that might prevent the emergence of superconductivity.