Magnetic-field-dependent ultrafast carrier dynamics and spin–lattice interaction in Au nanopillar/La0.67Sr0.33MnO3 film composites

We investigate the carrier and spin dynamics of nanocomposite thin films with Au nanopillars vertically aligned in the La0.67Sr0.33MnO3 matrix using ultrafast optical spectroscopy at 10 K in a magnetic field up to 6 T. The transient reflectivity measurements show two characteristic relaxation processes, which are attributed to the electron–phonon coupling and phonon-assisted spin–lattice interaction, respectively. The electron–phonon coupling constant is independent of the external magnetic field, while the spin–lattice dynamics are strongly influenced by the applied field. We demonstrate that the magnetic-field-induced modification of the spin–lattice interaction originates from a reduction in the magnetic entropy. The field-induced modification of the spin–lattice dynamics is further confirmed by the time-resolved Kerr rotation measurements. Our findings reveal the critical role of the magnetic field in the photo-induced dynamical interactions in nanocomposite films.