Abstract
The time-resolved photoreflectance and MOKE measurement systems are used to measure the carrier and spin dynamics of La0.7Ca0.3MnO3, a typical colossal magnetoresistance material (CMR). We have directly observed the transient behaviors of carrier and spin at different temperature and under differently external fields. They are evidenced that the spin relaxation time is faster than carrier relaxation time in this material. The relaxation processes of the spin are due to complex thermal equilibrium among the spin, electron, and lattice. The transient MOKE trace, which is independent of pumped polarization after the fastest relaxation time of spin at low temperature < Tc, will cool down the lattice temperature due to electron-spin interactions.