Non-Fermi surface nesting driven commensurate magnetic ordering in Fe-doped Sr$_2$RuO$_4$

TL;DR

Fe doping in Sr$_2$RuO$_4$ induces a stable commensurate magnetic order without significantly altering the Fermi surface nesting, revealing a new magnetic instability in this unconventional superconductor.

Contribution

This study demonstrates that Fe doping stabilizes a commensurate spin density wave in Sr$_2$RuO$_4$, independent of Fermi surface nesting changes.

Findings

Fe doping induces commensurate SDW order

Fermi surface nesting remains largely unchanged

Sr$_2$RuO$_4$ exhibits proximity to multiple magnetic instabilities

Abstract

Sr$_2$RuO$_4$, an unconventional superconductor, is known to possess an incommensurate spin density wave instability driven by Fermi surface nesting. Here we report a static spin density wave ordering with a commensurate propagation vector $q_c$ = (0.25 0.25 0) in Fe-doped Sr$_2$RuO$_4$, despite the magnetic fluctuations persisting at the incommensurate wave vectors $q_{ic}$ = (0.3 0.3 L) as in the parent compound. The latter feature is corroborated by the first principles calculations, which show that Fe substitution barely changes the nesting vector of the Fermi surface. These results suggest that in addition to the known incommensurate magnetic instability, Sr$_2$RuO$_4$ is also in proximity to a commensurate magnetic tendency that can be stabilized via Fe doping.