Enhancement of intrinsic magnetic damping in defect-free epitaxial Fe3O4 thin films

We have investigated the magnetic damping of precessional spin dynamics in defect-controlled epitaxial grown Fe3O4(111)/Yttria-stabilized Zirconia nanoscale films by all-optical pump-probe measurements. The intrinsic damping constant of the defect-free Fe3O4 film is found to be strikingly larger than that of the as-grown Fe3O4 film with structural defects. We demonstrate that the population of the first-order per- pendicular standing spin wave (PSSW) mode, which is exclusively observed in the defect-free film under sufficiently high external magnetic fields, leads to the enhancement of the magnetic damping of the uniform precession (Kittel) mode. We propose a physical picture in which the PSSW mode acts as an additional channel for the extra energy dissipation of the Kittel mode. The energy transfer from the Kittel mode to the PSSW mode increases as in-plane magnetization precession becomes more uniform, resulting in the unique intrinsic magnetic damp- ing enhancement in the defect-free Fe3O4 film.