Pressure and doping control of magnetic order and metallization in Ruddlesden-Popper La2NiO4

TL;DR

This study uses density functional theory to explore how pressure and doping influence magnetic order and electronic transitions in La2NiO4, revealing pressure-induced metallization and complex magnetic phase evolution relevant to nickelate superconductivity.

Contribution

It provides detailed insights into pressure and doping effects on magnetic and electronic properties of La2NiO4, highlighting unique behaviors compared to other nickelates.

Findings

Pressure induces insulator-metal transition at ~50 GPa.

Magnetic order remains robust up to 75 GPa under pressure.

Doping causes evolution from G-type to ferromagnetic order and metallization.

Abstract

The discovery of superconductivity in multilayer nickelates under pressure has intensified interest in understanding the magnetic and electronic properties of Ruddlesden-Popper nickelates. Using density functional theory with Hubbard corrections, we investigate the magnetic ground state, electronic structure evolution under pressure, and Sr-doping effects in La$_2$NiO$_4$. We find that at ambient pressure, tetragonal La$_2$NiO$_4$ exhibits G-type antiferromagnetic order with negligible interlayer magnetic coupling. Under hydrostatic pressure, the system undergoes a continuous insulator-metal transition at ~50 GPa while maintaining robust magnetic order up to 75 GPa, contrasting sharply with the rapid magnetic suppression in La$_3$Ni$_2$O$_7$. Sr doping induces a systematic evolution from G-type to A-type, to striped antiferromagnetic orders, and eventually to ferromagnetic order, accompanied by metallization. Furthermore, LaSrNiO$_4$ displays weak charge and orbital orders. These results reveal the unique pressure and doping effects of single-layer nickelates and provide insights into the magnetic mechanisms underlying nickelate superconductivity.