Intriguing magnetism of Fe monolayers on hexagonal transition-metal surfaces

TL;DR

This study uses first-principles calculations to explore how Fe monolayers exhibit diverse magnetic phases on different hexagonal transition-metal surfaces, influenced by substrate d-band filling and lattice frustration.

Contribution

It reveals the substrate-dependent magnetic phases of Fe monolayers, including novel AFM structures, due to variations in exchange coupling and geometric frustration.

Findings

Fe monolayers show different magnetic orders on hcp and fcc surfaces.

Exchange coupling varies from AFM to FM depending on substrate.

Unique AFM structures like 120-degree Neel and double-row-wise AFM are identified.

Abstract

Using first-principles calculations, we demonstrate that an Fe monolayer can assume very different magnetic phases on hexagonal hcp (0001) and fcc (111) surfaces of 4d- and 5d-transition metals. Due to the substrates' d-band filling, the nearest-neighbor exchange coupling of Fe changes gradually from antiferromagnetic (AFM) for Fe films on Tc, Re, Ru and Os to ferromagnetic on Rh, Ir, Pd, and Pt. In combination with the topological frustration on the triangular lattice of these surfaces the AFM coupling results in a 120-degree Neel structure for Fe on Re and Ru and an unexpected double-row-wise AFM structure on Rh, which is a superposition of a left- and right-rotating 90-degree spin spiral.