Enhanced Optical Response in Au Nanopillar/La0.67Sr0.33MnO3 Film Composites: Implications for Magnetooptical Devices

Abstract

Metal oxide vertically aligned nanocomposite thin films have been of considerable interest for hot-carrier-based light harvesting and active plasmonic applications. Herein, we present femtosecond pump–probe spectroscopy studies on a nanocomposite thin film with plasmonic Au nanopillars vertically aligned in a ferromagnetic La0.67Sr0.33MnO3 (LSMO) matrix. Our measurements reveal that the carrier decay of Au/LSMO films qualitatively follows that of pure LSMO with a two-component relaxation. In the presence of Au nanopillars, the charge generation within the LSMO film is enhanced by a factor of ∼40, and the spin–lattice relaxation time associated with demagnetization is substantially decreased from 259.6 to 7.7 ps. The enhanced nonequilibrium dynamics and energy transfer between the lattice and spin system in the Au/LSMO films can be well modeled using an extended three-temperature model. These Au/LSMO thin films can be potentially useful in ultrafast photoelectric and magnetooptical applications.