Improvement in magneto-optical properties of Bi-YIG particulate films by reduction in particle size

Bismuth substituted yttrium iron garnet particles were prepared by coprecipitation reaction and heat treatment. The coprecipitation was made by addition of an aqueous solution including cations in a NH₄ OH solution with keeping a pH value at 10.5 or 12.5. NaOH or NH ₄OH solution was added to keep the pH value constant during the coprecipitation reaction. The heat-treatment temperature required for the formation of a crystalline garnet phase decreased from 600 to 500°C compared with that for the particles synthesized by a rapid addition of the ammonia solution into the cation solution in the conventional method, leading to the reduction in their average crystallite size from 40 to 20 nm. The absorption loss decreased and the Faraday rotation was increased for particulate films using these particles, resulting in an improvement of a figure of merit from 2.56 to 4.80 degrees