Structural, magnetic and optical properties of Au/YIG, YIG/Au and Au/YIG/Au multilayer thin film stacks

Y3Fe5O12 shortly named YIG thin film and various form of Au and YIG thin film stacks have been grown on quartz substrate using both spin-coating and sputtering methods. The films are crystallized in cubic phase after heat treatments process that is optimized to avoid cracks on the surface. The thickness of the YIG layer measured by cross-section electron microscope imaging technique are found as about 80 nm for all samples. While the root-mean-square surface roughness of the YIG film is in sub-nanometer scale, it increases up to 2.86 nm by adding Au layer in the film structure. All films exhibit in-plane easy axis and low coercive field at room temperature. But, the saturation magnetization values of films decrease with Au layer. Whereas the optical transmission value is around 80% for YIG samples above 400 nm, it decreases dramatically with Au in the film stacks. The highest absorption coefficient value is found as similar to 20 x 10(4) cm(-1) in Q/Au/YIG structure. This strong absorption might come from the localized surface plasmon polaritons of Au noble metals in YIG structure because it enhances the electronic transition from crystal field splitting. As a result of these measurements, it is seen that the Au layer reduces the magnetization of the films, while increases the absorption rate significantly. Due to considerably low production cost of YIG in this work, it might open to commonly use of them in the magneto-optical devices.