Perpustakaan Digital ITB

A density functional study has been performed to investigate the effect of Hubbard energy, space group variations, and the Ca doping on electronic and magnetic properties of LaMnO3 systems. Density functional theory is used with the generalize gradient approximation (GGA) for exchange – correlation functional and Hubbard potential (Ueff) to consider strong electron correlation in d orbitals. The calculation parameter for LaMnO3 in cubic structure are 50 Ry cutoff energy and 8 x 8 x 8 K-point mesh, for orthorhombic system is 6 x 6 x 5 K-point mesh, for La1-xCaxMnO3 (x=0.25) are 40 Ry cutoff energy and 4x4x3 K-point mesh. As the results, all the LaMnO3 system exhibits the ferromagnetic half-metallic behaviors. The ferromagnetic behavior of cubic and orthorhombic system mainly comes from Mn3+ ions, while the Ca-doped system comes from mix Mn3+ and Mn4+ ions. In the cubic system, we find the crystal-field splitting at Mn 3d orbital without any Jahn-Teller distortion. All spin-up Mn 3d-t2g and almost spin down Mn 3d-t2g states are occupied and unoccupied, respectively. Furthermore, all-spin Mn 3d-eg states spread below and above the Fermi energy level (Ef). These results indicate the high-spin (HS) state at Mn 3d orbitals. Notably, the Jahn-Teller distortion lifts the degeneracy levels both t2g and eg, in which each sub-d states are located at different energy levels. By incorporating the Hubbard potential (GGA+Ueff), the magnetic moment and lattice parameter of all the system increase. For orthorhombic and Ca-doped system, the calculation removes the crystal field splitting and JT distortion, respectively. The calculation with Ueff do not change the magnetic property of all the system.