Optical and magneto-optical properties of magnetic nanocomposites FePt-SiO2.

Structural, magnetic, magnetotransport, optical, and magneto-optical properties of (FePt)1-X(SiO2)X thin films in as-deposited state and after annealing were investigated. Magneto-optical properties were measured in the transversal Kerr effect (TKE) geometry. Magneto-optical spectra in nanocomposites (FePt)1-X(SiO2)X depend greatly on volume fraction of metal and annealing conditions. The TKE reaches the maximum value for compositions close to the percolation threshold X≈57% in as-deposited samples, as well as a maximum of the magnetoresistance. After annealing at 700 °C the TKE value significantly increases and the maximum of the magneto-optical response is observed at X≈70%. The magneto-optical spectra transformation after annealing is mainly due to the disorder-order phase transitions in FePt granules, changes in the mean granular size, and alloy microstructure. The TKE spectra calculated in the framework of the effective medium approximation for as-deposited samples are in good agreement with the experiment. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]