Electronic structure and magneto-optical spectra of La sub(x)Sr sub(1-x)MnO sub(3) perovskites: Theory and experiment

The electronic structure and optical and magneto-optical Kerr (MOKE) spectra of La sub(x)Sr sub(1-x)MnO sub(3) (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 LaMnO sub(3) and La sub(0.75)Sr sub(0.25)MnO sub(3) 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 LaMnO sub(3) or right value of electron polarization at the Fermi level in ferromagnetic metallic La sub(1-x)Sr sub(x)MnO sub(3) 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 LaMnO sub(3) to the La sub(1-x)Sr sub(x)MnO sub(3).