Novel nanoparticle milling process for Bi-YIG dispersed transparent films

We developed a high-performance milling process with a grooved mill pot. The milling process is able to make highly transparent dispersed materials. Bi_1.8Y_1.2Fe₅O₁₂ nanoparticles were prepared with coprecipitation and annealing processes. The nanoparticle dispersed films were prepared with the milling process and a conventional process. The crystallite sizes of the Bi_1.8Y_1.2Fe₅O₁₂ particles in the milled films were 40-50 nm. These sizes were about half that of the films prepared by conventional process. The films containing the particles show high transparency. The light-absorption coefficients of the films were about half that of the films prepared by the conventional process. Magnetooptical properties were also improved. The milling process produces films with a high figure of merit, which is the value of Faraday rotation angle divided by light-absorption coefficient. The milling period was shorter than that of the conventional process.