Influence of surface plasmons on the Faraday effect in bismuth-substitutedyttrium iron garnet films

The Kerr rotation and ellipticity of Bi1.8Y1.2Fe5O12 films (Bi:YIG) with th e easy axis of magnetization perpendicular to the film plane was investigat ed in a Kretschmann setup at the wavelength 1.31 mum. The sample was coated by a thin Au film in order to excite plasmons at the free Au surface. An e llipsometric setup, supplemented with a magnetic field oriented perpendicul arly to the film plane was used to measure the reflected p and s components of an incoming p polarized wave. The phase difference between the outgoing p and s waves was found by an indirect procedure. A minimum in Kerr rotati on and a maximum in Kerr ellipticity could be observed at the surface plasm on resonance angle. Using the Berreman formalism, the experimental curves f or the prism/Bi:YIG/Au system could be reproduced by bulk optical constants of the constituents. The asymmetry of the ellipticity curve is demonstrate d to arise from a sudden variation in the phase. The effects of the field d istribution and the surface roughness are discussed. (C) 2001 American Inst itute of Physics.