Photoinduced transient thermoelectric effect in a perovskite manganite Pr0.67Sr0.33MnO3 film

Pulsed laser-induced transient thermoelectric effect (TTE) for perovskite m anganite Pr0.67Sr0.33MnO3 thin films has been measured under de electric an d magnetic fields. Without any external fields, a photoinduced TTE voltage is small (similar to 0.5 mV). When an electric field is applied, its magnit ude enhances appreciably and decays exponentially with two relaxation times , but its sign is changed by varying temperature. The TTE voltage and its s ign are also varied by applying magnetic field, from which the Curie temper ature is determined. Based on the available band model of this material, we have discussed a possible mechanism for the observed TTE signals. The TTE phenomenon is primarily due to the formation of a bipolar state of photogen erated electrons and holes, which reflect strongly on the characteristic ba nd structure in the paramagnetic and ferromagnetic phases. Its decay proces s is a recombination of the electron-hole pairs through some recombination centers, in which the Jahn-Teller or polaron effect is found to be apprecia ble near the Curie temperature. [S0163-1829(99)01119-4].