Structural and magnetic properties of FeMn$_x$ ($x=$1...6) chains supported on Cu$_2$N / Cu (100)

TL;DR

This study investigates the structural, electronic, and magnetic properties of FeMn$_x$ chains on Cu$_2$N/Cu (100) using STM, DFT, and model Hamiltonian approaches, revealing how chain size influences magnetic interactions and anisotropy.

Contribution

It provides a comprehensive analysis of FeMn$_x$ chains, including magnetic coupling and anisotropy parameters, combining experimental STM data with theoretical DFT and Hamiltonian modeling.

Findings

Magnetic properties evolve with chain length from 1 to 6 atoms.

Exchange-coupling constants and anisotropy parameters are quantified.

Theoretical results agree with experimental magnetic excitation energies.

Abstract

Heterogeneous atomic magnetic chains are built by atom manipulation on a Cu$_2$N/Cu (100) substrate. Their magnetic properties are studied and rationalized by a combined scanning tunneling microscopy (STM) and density functional theory (DFT) work completed by model Hamiltonian studies. The chains are built using Fe and Mn atoms ontop of the Cu atoms along the N rows of the Cu$_2$N surface. Here, we present results for FeMn$_x$ ($x$=1...6) chains emphasizing the evolution of the geometrical, electronic, and magnetic properties with chain size. By fitting our results to a Heisenberg Hamiltonian we have studied the exchange-coupling matrix elements $J$ for different chains. For the shorter chains, $x \leq 2$, we have included spin-orbit effects in the DFT calculations, extracting the magnetic anisotropy energy. Our results are also fitted to a simple anisotropic spin Hamiltonian and we have extracted values for the longitudinal-anisotropy $D$ and transversal-anisotropy $E$ constants. These parameters together with the values for $J$ allow us to compute the magnetic excitation energies of the system and to compare them with the experimental data.