Substrate-induced antiferromagnetism of an Fe monolayer on the Ir(001) surface

TL;DR

This study uses ab initio calculations to show that a Fe monolayer on Ir(001) surface becomes antiferromagnetic due to substrate-induced effects, with the magnetic order influenced by layer relaxation and interatomic interactions.

Contribution

It reveals how substrate-induced relaxation stabilizes antiferromagnetism in Fe/Ir(001), contrasting with unrelaxed ferromagnetic states and compares this behavior to Fe/Rh(001).

Findings

Antiferromagnetism is stabilized by decreased Fe-Ir layer spacing.

Unrelaxed Fe/Ir(001) favors ferromagnetism.

Possible complex spin spiral ground state.

Abstract

We present detailed ab initio study of structural and magnetic stability of a Fe-monolayer on the fcc(001) surface of iridium. The Fe-monolayer has a strong tendency to order antiferromagnetically for the true relaxed geometry. On the contrary an unrelaxed Fe/Ir(001) sample has a ferromagnetic ground state. The antiferromagnetism is thus stabilized by the decreased Fe-Ir layer spacing in striking contrast to the recently experimentally observed antiferromagnetism of the Fe/W(001) system which exists also for an ideal bulk-truncated, unrelaxed geometry. The calculated layer relaxations for Fe/Ir(001) agree reasonably well with recent experimental LEED data. The present study centers around the evaluation of pair exchange interactions between Fe-atoms in the Fe-overlayer as a function of the Fe/Ir interlayer distance which allows for a detailed understanding of the antiferromagnetism of a Fe/Ir(001) overlayer. Furthermore, our calculations indicate that the nature of the true ground state could be more complex and display a spin spiral-like rather than a c(2x2)-antiferromagnetic order. Finally, the magnetic stability of the Fe monolayer on the Ir(001) surface is compared to the closely related Fe/Rh(001) system.