Magnetic behavior of yttrium–iron–garnet nanoparticles dispersed in glass composites

Abstract

By absorbing amorphous yttrium–iron–garnet (YIG) nanoparticles into nanosized pores of a controlled pore glass (CPG) followed by heat treatment, we synthesized YIG nanocrystal-dispersed glass composites. In a sample which was prepared with a 300 nm pore size CPG and heat treated at 800 °C for 2 h, almost all the amorphous YIG nanoparticles transformed to YIG nanocrystals. The mass fraction of YIG was estimated to be 4.7% from the measured saturation magnetization. In a sample which was prepared from a 49 nm pore size CPG with the same heat treatment, the amount of YIG was estimated to be only 0.54%. Magnetization measurements of different samples revealed that heat treatment at higher temperatures or for longer times resulted in reactions of the YIG particles with the SiO2 of the CPG, and the composites became paramagnetic. However, even in those samples, large initial magnetic susceptibilities were measured, implying the presence of a small amount of unreacted YIG nanocrystals.