Observation of the crystal-field splitting related to the Mn-3d bands in spinel-LiMn2O4 films by optical absorption

Mn 3d bands in spinel-LiMn2O4 films, synthesized on SiO2-glass substrates by a sol-gel method, were studied using an optical absorption method. Two absorption peaks were observed at around 1.63 and 2.00 eV at room temperature. These peaks were associated with two d-d transitions: One is the Mn t(2g) to the lower Mn e(g) bands transition and the other the Mn t(2g) to the upper Mn e(g) bands one. A large absorption was also observed above 3.0 eV, indicating a transition from the O 2p valence band to the Mn 3d bands. The d-d transitions showed the blueshifts of 20-30 meV at 77 K comparing with those at room temperature. The observed electronic structure was consistent with the calculated one. (C) 2000 American Institute of Physics. [S0003- 6951(01)04101-8].