Magnetization-induced optical second-harmonic generation and local   surface plasmons in magnetic $Co_x Ag_{1-x}$ nanogranular films
  Spectroscopy of magnetization-induced second-harmonic generation (MSHG) is studied in magnetic Co$_{x}$Ag$_{1-x}$ granular films containing Co nanoparticles. A strong resonance of the magnetic contrast of the second-harmonic generation (SHG) intensity is observed in the two-photon energy range from 3,8 eV to 4,5 eV. The local surface plasmons exited in magnetic Co nanogranules in this spectral range assist MSHG and are responsible for a significant enhancement of the SHG magnetic contrast due to the resonances of local optical fields. 
E.M. Kim, T.V. Murzina, A.F. Kravets, M. Inoue, G. Marowsky, O.A.   Aktsipetrov