Calculation of Exchange and Anisotropy Energies in Single molecule magnets

by Yu, Yongxue

In this thesis, we have studied two single molecule magnets [Co4(hmp)4(CH3OH)4Cl4] and [Ni4(hmp)4(CH3OH)4Cl4] using Density-Functional-Theory code NRLMOL with generalized gradient approximation (GGA). Both exchange integrals and anisotropy parameters are calculated for these two molecules. We find that Co-based molecule has higher anisotropy energy than Ni-based one although these two molecules have the same geometry and Co and Ni in the same environment. It can be seen that both the magnetic moments and zero-field splitting parameter D are critical to determine the anisotropy energy. Most of our calculated results are in good agreement with experiments.