Nonlinear optical spectroscopy of (La$_{0.6}$Pr$_{0.4}$)$_{0.7}$Ca$_{0.3}$MnO$_3$ manganite

The electronic structure of doped orthorhombic (La$_{0.6}$Pr$_{0.4})_{0.7}$Ca$_{0.3}$MnO$_3$ manganite is studied using the second optical harmonic generation method. The analysis of the frequency and polarization dependence of the intensity related to the second harmonic demonstrates that the applied magnetic field stimulates a transition of spin-polarized electrons from the d orbitals of Mn ions to the p orbitals of O$_2$ ligands. The manifestation of such transition in the orthorhombic RMnO$_3$ manganite with the distorted crystal lattice is attributed to the dipole-forbidden electronic transitions arising in the applied magnetic field. The mechanism of magnetooptical activity induced by the charge transfer between Mn and O ions is discussed.