Possible magnetic phases in two-band systems with different dimensionality

The ground states of the molecular conductors (Me4Z)[Pd(dmit)2]2, which have strong dimerization and two bands with different dimensionality, have been studied based on the Hartree-Fock approximation. The results indicate that two different magnetic orders appear depending on both the energy difference between the two bands and the strength of the Coulomb interaction. To clarify the origin of the magnetic orders, exchange interactions between dimers have been calculated within the second-order perturbation theory with respect to the inter-dimer transfer integrals. We have found that the different magnetic orders are due to the different symmetry of the molecular orbitals.