Modelling the magnetic properties of 1D arrays of FePc molecules

TL;DR

This study models the magnetic behavior of one-dimensional FePc molecular chains, revealing anisotropic exchange interactions, single ion anisotropy, and the presence of magnetic solitons, supported by DFT and Monte Carlo simulations.

Contribution

It introduces a generalized Heisenberg model with parameters derived from DFT calculations to explain magnetic phenomena in FePc chains, including non-saturation of magnetization and soliton presence.

Findings

Anisotropic exchange interaction J identified

Easy plane single ion anisotropy D observed

Magnetic solitons are present and easily excited

Abstract

We investigate the magnetic properties of Fe Phthalocyanines (FePc) that are experimentally arranged in quasi one-dimensional chains when they are grown in thin films or powders. By means of DFT calculations we reproduce the structural parameters found in experiments, and then we build a generalized Heisenberg magnetic model with single ion anisotropy, and calculate its parameters. The results show a anisotropic exchange interaction $J$ between FePc molecules, and an easy plane single ion anisotropy $D$. By means of Monte Carlo simulations, with this model, we found an explanation to the non-saturation of the magnetization found at high fields, which we interpret is due to the anisotropic exchange interaction $J$. Finally, we also investigate the presence of magnetic solitons versus temperature and magnetic field. This results provide additional evidence that FePc is a soliton bearing molecular compound, with solitons easily excited mainly in the molecular $xy$ plane.