Temperature Dependent Cation Distribution in Tb2Bi1Ga1Fe4O12

Abstract

In this study, heavy rare earth garnet <TEX>$Tb_2Bi_1Ga_1Fe_4O_{12}$</TEX> powders were fabricated by a sol-gel and vacuum annealing process. The crystal structure was found to be single-phase garnet with a space group of Ia3d. The lattice constant <TEX>$a_0$</TEX> was determined to be 12.465 <TEX>${\AA}$</TEX>. From the analysis of the vibrating sample magnetometer (VSM) hysteresis loop at room temperature, the saturation magnetization and coercivity of the sample are 7.64 emu/g and 229 Oe, respectively. The N<TEX>$\acute{e}$</TEX>el temperature(<TEX>$T_N$</TEX>) was determined to be 525 K. The M<TEX>$\ddot{o}$</TEX>ssbauer spectrum of <TEX>$Tb_2Bi_1Ga_1Fe_4O_{12}$</TEX> at room temperature consists of 2 sets of 6 Lorentzians, which is the pattern of single-phase garnet. From the results of the M<TEX>$\ddot{o}$</TEX>ssbauer spectrum at room temperature, the absorption area ratios of Fe ions on 24d and 16a sites are 74.7% and 25.3%(approximately 3:1), respectively. These results show that all of the non-magnetic Ga atoms occupy the 16a site by a vacuum annealing process. Absorption area ratios of Fe ions are dependent not only on a sintering condition but also on the temperature of the sample. It can then be interpreted that the Ga ion distribution is dependent on the temperature of the sample. The M<TEX>$\ddot{o}$</TEX>ssbauer measurement was carried out in order to investigate the atomic migration in <TEX>$Tb_2Bi_1Ga_1Fe_4O_{12}$</TEX>.