Tight-binding coherent potential approximation study of ferromagneticLa2/3Ba1/3MnO3

Abstract

The local-spin-density band structure of a virtual-crystal model of ferromagnetic La${}_{2/3}$Ba${}_{1/3}$MnO${}_{3}$, reported earlier by Pickett and Singh [Phys. Rev. B 53, 1146 (1996)], has been fit to an accurate orthogonal tight-binding (TB) model. This TB Hamiltonian has spin-independent hopping parameters, and the exchange splitting is confined solely to the Mn on-site parameters ${\ensuremath{\varepsilon}}_{{t}_{2g}\ensuremath{\downarrow}}\ensuremath{-}{\ensuremath{\varepsilon}}_{{t}_{2g}\ensuremath{\uparrow}}$=3.44 eV and ${\ensuremath{\varepsilon}}_{{e}_{g}\ensuremath{\downarrow}}\ensuremath{-}{\ensuremath{\varepsilon}}_{{e}_{g}\ensuremath{\uparrow}}$=2.86 eV. The 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 $p\ensuremath{\sigma}$ and $p\ensuremath{\pi}$ states are allowed distinct site energies, and the derived crystal-field splitting is ${\ensuremath{\varepsilon}}_{p\ensuremath{\pi}}\ensuremath{-}{\ensuremath{\varepsilon}}_{p\ensuremath{\sigma}}$ = 1.47 eV. Local Mn $d$ site energy disorder, arising from the random distribution of La${}^{3+}$ and Ba${}^{2+}$ ions, has been treated within the TB coherent potential approximation. The intrinsic resistivity in the fully polarized phase from this charge disorder is estimated to be 15 $\ensuremath{\mu}\ensuremath{\Omega}\mathrm{cm}$.