Magnetic-order induced spectral-weight redistribution in La0.7 (Sr,Ca) 0.3 MnO3
Artikel i vetenskaplig tidskrift, 2006
We present the optical and magneto-optical characterization of La0.7 (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 ΔJT ≈0.8 eV, JH >0.8 eV, U>2.9 eV, and Δ≤2.2 eV.