Magnetic-order induced spectral-weight redistribution in La0.7(Sr,Ca)0.3MnO3

We present the optical and magneto-optical characterization of La-0.7(Sr,Ca)(0.3)MnO3 at temperatures 25 K <= T <= 470 K. The metal-insulator transition is accompanied by a magnetic-order induced spectral-weight redistribution within 0.5-5.5 eV. Relating the kinetic energy of superexchange and double-exchange models to the optical spectral weight allows the distinction of Mn intersite from O2p -> Mn3d charge-transfer excitations. We infer that with decreasing temperature, the lower Hubbard band approaches the in-gap states by a reduction of the Jahn-Teller energy causing the metal-insulator transition. We estimate Delta(JT)approximate to 0.8 eV, J(H)> 0.8 eV, U > 2.9 eV, and Delta <= 2.2 eV.