Antiferromagnetism and onset of Superconductivity in Lanthanum Nickelates

Abstract

ABSTRACTMagnetic moment and resistivity measurements are summarized for the La2−xSrxNiO4 system. They show that the system undergoes a structural phase separation below 70 K. The majority of the sample is antiferromagnetic (AF) below 650 K (for x = 0) or 20 K (for x = 0) or 20 K (for x ≃ 0.2 while the minority phase (≤1% at 4.2 K) is superconducting (SC). An analysis of the results leads to the conclusion that SC and AF coexist in the minority part of the sample; the pairing takes place between 2p holes which propagate through a lattice containing localized 3d moments which, in the ground state, are ordered antiferromagnetically.