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The spin damping behavior of the bismuth-substituted yttrium iron garnets (BixY3−xFe5O12) prepared by the coprecipitation process was investigated using the ferromagnetic resonant (FMR) in this study. By analyzing the FMR responses, the spin damping coefficient of the x=0.25–1.25 in polycrystalline Bi:YIG (yttrium aluminum garnet) samples was obtained from the 3 dB linewidth of their FMR spectra. The data demonstrated that the damping coefficient started from 3.21×10−3 for x=0.25 and went to its minimum value of 0.31×10−3 for x=0.75. However, the damping coefficient enhanced to 8.55×10−3 with increasing of the bismuth concentration to x=1.25. The results revealed that the spin damping behavior of the Bi:YIG garnets was strongly dependent on a YFeO3 (111) phase.

The magnetic-induced dielectric responses of BiFeO3 (BFO) thin films were measured at the X-band microwave frequency ranged from 7 to 12.5 GHz. The measurement was given initially by a high-precision cavity microwave resonator without magnetic field. Both the real and imaginary parts of the permittivity showed its dielectric property as a function of the measuring frequency. The X-band dielectric responses of the BFO thin film were then measured by a controlled magnetic field at room temperature. The data demonstrated up to 2.2% dielectric tunability by using only 3.46 kOe magnetic field at TE107 mode (9.97705 GHz).

Li0.5Fe2.5−xMgxO4 (0≦x≦1.0) powders with small and uniformly sized particles were successfully synthesized by microwave-induced combustion using lithium nitrate, ferric nitrate, magnesium nitrate, and carbohydrazide as the starting materials. This process takes only a few minutes to obtain as-received Mg-substituted lithium ferrite powders. The results revealed that the lattice constant increases nonlinearly with increasing Mg content in the Li0.5Fe2.5−xMgxO4 specimens. Moreover, the magnetic properties of Mg-substituted lithium ferrite were also strongly affected by Mg concentration. The saturation magnetization (Ms) of 71.1 emu/g was found at Li0.5Fe2.5O4 specimen. As increased Mg content, the saturation magnetization (Ms) and remanent magnetization (Mr) decreased significantly. This is ascribed to the fact that as Mg content increases, A-O-B (where A represents tetrahedral sites and B represents octahedral sites in ferrite of the spinel type) interactions become weak, and consequently B-O-B interaction...