Antiferromagnetic spin fluctuations and proximity to a quantum critical point inSr2RuO4

Abstract

Spin-density functional calculations are used to investigate the proximity to antiferromagnetism and the effects of partial Ti substitution in ${\mathrm{Sr}}_2\mathrm{Ru}{\mathrm{O}}_4$. Ti is found to enter the lattice as ${\mathrm{Ti}}^{4+}$ with only a small relaxation of the neighboring O ions. The Ti disrupts the $\mathrm{Ru}-\mathrm{O}-\mathrm{Ru}$ chains, leading to an increase in the local density of states, and thereby favors moment formation on the neighboring Ru sites. Supercell calculations and frozen spin-wave calculations show a weak antiferromagnetic instability at the Fermi surface nesting vector implying nearness to a quantum critical point. Properties of ${\mathrm{Sr}}_2\mathrm{Ru}{\mathrm{O}}_4$ are discussed in relation to these results.