AVS 50th International Symposium
    Magnetic Interfaces and Nanostructures Wednesday Sessions
       Session MI-WeP

Paper MI-WeP5
Ultrafast Laser Measurements of Electron and Spin Dynamics in Half-metallic CrO@sub 2@ Thin Films

Wednesday, November 5, 2003, 11:00 am, Room Hall A-C

Session: Poster Session
Presenter: H. Huang, College of William and Mary
Authors: H. Huang, College of William and Mary
K. Seu, College of William and Mary
A.C. Reilly, College of William and Mary
W.F. Egelhoff, National Institute of Standards and Technology
Y. Kadmon, National Institute of Standards and Technology
Correspondent: Click to Email
Half-metallic ferromagnets are an important class of materials in which one spin state is conducting while the other has a semiconductor-like gap. While evidence of half-metallic behavior has been found, there are still many questions regarding the bandstructure and dynamics in these materials. Ultrafast laser pump-probe techniques have shown great promise for elucidating such information in a variety of materials. Recently, such pump-probe techniques have been applied to study spin dynamics@footnote 1@ in Sr@sub 2@FeMoO@sub 6@ and coherent magnetization rotation@footnote 2@ in CrO@sub 2@. We will present measurements of charge and spin dynamics in half-metallic CrO@sub 2@ thin films by ultrafast laser pump-probe reflection, transmission and MOKE experiments as a function of temperature and energy (wavelength). We find that the pump-probe reflection and transmission consist of components simlar to those seen in the other half-metallic systems such as LCMO and Sr@sub 2@FeMoO@sub 6@: An initial fast peak which decays within ~ 1 ps, and a longer component with a rise of ~ 10 ps and a decay time of ~ 500 ps. This may indicate similar mechanisms for these systems. We attempt to correlate the temperature dependence with the two-order-of-magnitude increase in resistivity with temperature that is taken as a signature of the half-metallic behavior. The wavelength dependence is used to explore the bandstructure. For example, we observe different electron and spin dynamics for excitation energies of 1.5 eV and 3 eV, corresponding to the energies of excitation within the conducting spin-up band and across the gap for the spin-down state. @FootnoteText@ @footnote 1@T. Kise et al., Phys. Rev. Lett., 85, 1986 (2000). @footnote 2@Qiang Zhang et al., Phys. Rev. Lett., 89, 177402 (2002).