Magneto-optical properties of Yttrium Iron Garnet (YIG) thin films elaborated by radio frequency sputtering

摘要

Thin films of Yttrium Iron Garnet (YIG) are grown by radio frequency magnetron non reactive sputtering system. Thin films are crystallised by heat-treatment to obtain magneto-optical properties. On quartz substrate, the network of cracks observed on the annealed samples can be explained by the difference between the thermal expansion coefficient of substrate and YIG. The Faraday rotation of thin films is measured with a classical ellipsometric system based in transmission which allows us to obtained an accuracy of 0.01°. We studied the variation of Faraday rotation versus the applied magnetic field. The variation of the Faraday rotation is the same that this obtained by VSM (vibrating sample magnetometer) analysis. With a quartz substrate, maximum Faraday rotation is observed to be 1900°/cm at the wavelength of 594 nm for an annealing of 740°C. The variation of the Faraday rotation versus the wavelength is studied. The obtained values are comparable to those of the literature for the bulk material. In order to eliminate the stress due to the heat-treatment, we made some films on Gadolinium Gallium Garnet (GGG) which thermal expansion coefficient is near than the YIG one. The material crystallises with no cracks and the Faraday effect is equivalent.