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Zusammenfassung:
The electronic structure and optical and magneto-optical Kerr (MOKE) spectra of LaxSr1-xMnO3 (x = 0.0, 0.25) perovskites have been investigated experimentally and theoretically from first principles, using the fully relativistic Dirac linear MT-orbital band structure method in the local spin density approximation (LSDA) as well as within the LSDA + U approach. It is shown that the ab initio calculations reproduce well the experimental spectra and make it possible to explain the microscopic origin of the LaMnO3 and La0.75Sr0.25MnO3 optical and magneto-optical response in terms of interband transitions. We found that the electrons in close vicinity to the Fermi level are strongly correlated. To produce the correct energy gap in the LaMnO3 or right value of electron polarization at the Fermi level in ferromagnetic metallic La1-xSrxMnO3 doped alloys one has to take into account strong Coulomb correlations. On the other hand, the electronic structure and optical and MOKE spectra can be described satisfactorily in terms of LSDA energy bands in a wide energy range beyond close vicinity of the Fermi level. The Coulomb correlations are reduced in transition from the LaMnO3 to the La1-xSrxMnO3.
