Structural Effects on the Matgnetic Character of Yttrium-Iron-Garnet-Nanoparticles Dispersed in Glass Composites
S Taketomi, Alexander J. Shapiro, Robert D. Shull
By absorbing amorphous yttrium iron garnet (YIG) nanoparticles into the nanometer pores of the sponge-like structure of porous silica glass (controlled pore glass or CPG) followed by heat treatment, we obtained dispersed-nanocrystal/glass composites. We prepared samples with different external heat treatments: (a) low temperature long time calcination (700 C. 2 hours) and (b) high temperature short time calcination (1000 C, 0.1 hours). From the difference between the secondary electron image in a field emission scanning electron microscope (FESEM) and the back-scattered electron image of the same sample surface area, it is concluded that the nanoparticles were imbedded just beneath the surface of the CPG granules. This speculation was confirmed by the cross sectional back-scattered electron image in the FESEM of the sample. In this picture the nanparticles with a size distribution from 20 nm to 40 nm were monodispersed in a 2 m thick shell of fused glass and inside this shell, the inner core of CPG granules preserved their sponge-like structure and contained no nanoparticles. The powder X-ray diffraction revealed that the synthesized nanoparticles were dominantly -Fe2O3, however, many small diffraction peaks consistent with those for Fe5Y3O12 and FeYO3, were also observed. Magnetization hysteresis loop curves revealed that the high temperature heat-treated samples were paramagnetic, while the low-temperature heat-treated sample was a mixture of a small amount of ferro- or ferrimagnetic materials with a majority of paramagnetic material.
, Shapiro, A.
and Shull, R.
Structural Effects on the Matgnetic Character of Yttrium-Iron-Garnet-Nanoparticles Dispersed in Glass Composites, Journal of Applied Physics
(Accessed February 26, 2024)