Spin density wave in the bilayered nickelate La3Ni2O7−δ at ambient pressure

Abstract

The recent discovery of high-temperature superconductivity in high-pressurized La3Ni2O7−δ has garnered significant attention. Using density functional theory, we investigate the magnetic properties of La3Ni2O7−δ at ambient pressure. Our calculations suggest that with δ = 0, the double spin stripe phase is favored as the magnetic ground state. Oxygen vacancies may effectively turn nearest Ni spins into charge sites. Consequently, with moderate δ values, our theoretical magnetic ground state exhibits characteristics of both double spin stripe and spin-charge stripe configurations, providing a natural explanation to reconcile the seemingly contradictory experimental findings that suggest both the configurations as candidates for the spin-density-wave phase. With higher δ values, we anticipate the ground state to become a spin-glass-like noncollinear magnetic phase with only short-range order. The oxygen vacancies are expected to significantly impact the magnetic excitations and the transition temperatures TSDW. Notably, the magnetic ordering also induces concomitant charge ordering and orbital ordering, driven by spin-lattice coupling under the low symmetry magnetic order. We further offer a plausible explanation for the experimental observations that the measured TSDW appears insensitive to the variation of samples and the lack of direct evidence for long-range magnetic ordering.