Abstract
The magneto-optical properties of a -thick sample having a Curie temperature are investigated by time-resolved pump-probe and continuous-wave (cw) midinfrared transmittance spectroscopies. The pump pulses are linearly polarized and have a energy, a width, and a fluence. They produce a thermally driven demagnetization process in the hundreds of picosecond time scale. A three-temperature model based on one-dimensional diffusion equations was developed to compute the carrier, lattice, and spin temperatures in the material. We observed that an average photoinduced spin temperature increase near leads to an augmentation of the Mn acceptor impurity binding energy in the range of . cw absorption measurements were performed at temperatures ranging from , and a nonmonotonic temperature dependence of the position of the midinfrared absorption peak is found that is consistent with the increased binding energy observed by time-resolved measurements. The variation of the sample resistivity with temperature is phenomenologically related to the optical measurements. Results are compatible with a polaron percolation model of ferromagnetism.
2 More- Received 10 May 2007
DOI:https://doi.org/10.1103/PhysRevB.76.195323
©2007 American Physical Society