TIGHT-BINDING COHERENT-POTENTIAL APPROXIMATION STUDY OF FERROMAGNETICLA2 3BA1/3MNO3/

The local-spin-density band structure of a virtual-crystal model of fe rromagnetic La2/3Ba1/3MnO3, reported earlier by Pickett and Singh [Phy s. Rev. B 53, 1146 (1996)], has been fit to an accurate orthogonal tig ht-binding (TB) model. This TB Hamiltonian has spin-independent hoppin g parameters, and the exchange splitting is confined solely to the Mn on-site parameters epsilon(t2g down arrow) - epsilon(t2g up arrow) = 3 .44 eV and epsilon(eg down arrow) - epsilon(eg up arrow) = 2.86 eV. Th e crystal-field splitting, as reflected in the Mn d energies, is 1.77 eV for majority spin and 1.19 eV for minority spin. Oxygen p sigma and p pi states are allowed distinct site energies, and the derived cryst al-field splitting is epsilon(p pi) - epsilon(p sigma) = 1.47 eV. Loca l Mn d site energy disorder, arising from the random distribution of L a3+ and Ba2+ ions, has been treated within the TB coherent potential a pproximation. The intrinsic resistivity in the fully polarized phase f rom this charge disorder is estimated to be 15 mu Ohm cm.