Laser induced dynamic spectral weight transfer in La0.7Ca0.3MnO3

We report on optical pump-probe measurements at 1.5 eV and 3 eV on the colo ssal magnetoresistance material La0.7Ca0.3MnO3. The material response is de termined in the femtosecond to the nanosecond temporal regimes. By analyzin g the absorption and refractive dynamics within the Kramers-Kronig transfor mations we demonstrate dynamic spectral weight transfer from the intraband Drude component to the interband transitions. This spectral transfer and it s strongly temperature dependent dynamics are discussed in the framework of photoinduced demagnetization due to the exchange of energy and thermal equ ilibration among the electronic, lattice and spin systems. This effect is o bserved in other manganites with different transition temperatures. The mea sured dynamics are found to be insensitive to the excitation photon energy. (C) 2000 Elsevier Science B.V. All rights reserved.