Growth and magnetic behavior of bismuth substituted yttrium iron garnet nanoparticles

Crystal growth and the magnetic properties of bismuth substituted yttrium iron garnet (Bi-YIG) nanoparticles were studied with particular focus on the bismuth composition dependence of the magnetic properties of the particles and the effects of annealing on the garnet phase formation. The Bi-YIG nanoparticles of 47-67 nm in size can be chemically synthesized when they are annealed at 650-850 degrees C. Both the lattice constant and the magnetization of the garnet nanoparticles linearly increase when the bismuth composition in the Bi-YIG particles increases. We have found that chemically synthesized nanoparticles transform from the amorphous to the garnet phase when annealed at temperatures below 650 degrees C, while the onset of magnetic moment of iron in the garnet nanoparticles is observed slightly above 650 degrees C. According to Mossbauer effect measurements, the hyperfine fields of Fe-57 at the tetrahedral and octahedral sites in the garnet are 39 and 48 T, respectively.