Nonlinear optical diagnostic of semimagnetic semiconductors Pb1−xYbxX (X = S, Se, Te)

Nonlinear optical measurements were performed to elucidate the influence of magnetic ions on the behavior of charge carriers in magnetic semiconductors—Pb1−xYbxX (X = S, Se, Te at x = 1–3%). It was shown that nonlinear optical methods could be used as sensitive tools for investigations of electron–phonon anharmonicity near low-temperature semiconductor–insulator phase transitions. There exists a difference between surface and bulk-like contributions to the nonlinear optical effects. It was shown that only low-temperature Two Photon Absorption (TPA) oscillator may be related to the number of the electron–phonon anharmonic modes responsible for the observed phase transformation. The explanation of the anomalous temperature dependences is given in accordance with dipole momentum's behaviors determined by low-temperature spin–spin interactions and by electron–phonon anharmonic interactions. We have discovered that low-temperature dependence of specific heat of Pb1−xRxTe (R = Yb, Pr with x = 3% and 1.6%, respectively) exhibits a non-magnetic order caused by large electron–phonon contributions and structural disorder effects.