Enhanced Optical Response in Au Nanopillar/La_0.67Sr_0.33MnO₃ 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 La 0.67 Sr 0.33 MnO 3 (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.