Effects of Al Substitution on Dielectric Response and Magnetic Behavior of Yttrium Iron Garnet Ceramics

Structure, dielectric response, and magnetic properties of Y3Fe5-xAlxO12 (x = 0, 0.5, 1, 2, and 3) ceramics were investigated. X-ray diffraction (XRD) patterns indicate a single phase with garnet structure in space group Ia3d for all sintered samples. Rietveld refinement of XRD data suggest that Al3+ substitutes for Fe3+ at tetrahedral sites. All the samples show a giant dielectric response which originates from the charge carrier hopping between the Fe2+ and Fe3+. The activation energy of the hopping process increases with increasing Al substitution. The a-d super-exchange interaction becomes weak as the content of Al increases, which results in the decrease of saturation magnetizations and magnetic ordering temperatures.