Modeling the Magnetic Properties of 1D Arrays of FePc Molecules

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 density functional theory 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 an 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 find an explanation to the nonsaturation of the magnetization found at high fields, which we interpret to be due to the anisotropic exchange interaction J. Finally, we also investigate the presence of magnetic solitons versus temperature and magnetic field. These results provide additional evidence that FePc is a soliton-bearing molecular compound, with solitons easily excited mainly in the molecular xy plane.