The electronic structure of organic-inorganic hybrid compounds: (NH4)(2)CuCl4, (CH3NH3)(2)CuCl4 and (C2H5NH3)(2)CuCl4

Hybrid organic-inorganic compounds are an intriguing class of materials that have been experimentally studied over the past few years because of a potential broad range of applications. The electronic and magnetic properties of three organic-inorganic hybrid compounds with compositions (NH4)(2)CuCl4, (CH3NH3)(2)CuCl4 and (C2H5NH3)(2)CuCl4 are investigated for the first time with density functional theory plus on-site Coulomb interaction. A strong Coulomb interaction on the copper causes a relatively weak exchange coupling within the layers of the octahedral network, in good agreement with experiment. The character of the exchange interaction (responsible for magnetic behavior) is analyzed. The calculations reveal that (C2H5NH3)(2)CuCl4 has the strongest Jahn-Teller (JT) distortion in comparison with the two other compounds. The easy axis of magnetization is investigated, showing a weak anisotropic interaction between inter-layer Cu2+ ions in the (C2H5NH3)(2)CuCl4 structure. Orbital ordering is concluded from our partial density of states calculations: a cooperation of the JT distortion with an antiferro-distortive pattern.