The yttrium iron garnet（YIG） samples are prepared at different temperatures from 900℃ to 1300℃ by the metalorganic decomposition（MOD） method. The chemical composition and crystal structure of the samples are studied by scanning electron microscope（SEM）, XRD, and Mossbauer spectrometer. It is shown that the ratio of ferric ions on two types of sites, the octahedral and the tetrahedral, is increased with the sintering temperature. At 1300℃, the pure garnet phase has been obtained, in which the ferric ions ratio is 2：3 leading to the minimum magnetic coercivity and maximum saturation magnetization. These results provide a route to synthesize pure YIG materials as the basic materials used in various spintronics applications.
The influence of theα-decay radionuclide layer(the energy ofα-particles are 5.45 Me V)on the radar cross section(RCS)of sphere objects was calculated under different radioactivities,frequencies,and sphere radii.When the sphere radius is smaller than 50 cm,the tendency of the electron densities of the plasma slab is to ascend first and then descend,and the typical maximum electron densities with a radioactivity of 10 Ci/cm2raises from 7.02×1010to 1.76×1011when the sphere radii increases from 10 to 300 cm.The average data of a normalized RCS of a sphere with radius of 12.5 cm,which is coated with a radionuclide layer with different radioactivities are-0.35,-0.50,-0.79 and-1.13 d B when the radioactivity is 1,2,5 and 10 Ci/cm2,respectively.
A new material is prepared by impregnating the expanded graphite(EG) into ethanol solutions of metal acetate and then drying and reducing it in H2.It contains the EG and the nanoparticles of the magnetic Ni–Fe alloy for the electromagnetic shielding.Its morphology,phase structure,magnetic properties,and electromagnetic shielding effectiveness(SE) are investigated in our experiment.It shows that the morphology,the phase structure,and the magnetic property of the composite can be modified by altering the Ni content in the alloy nanoparticles.Interestingly,the SE can be enhanced to 54–70 d B at low frequencies(300 kHz–10 MHz) by dispersing the magnetic nanoparticles onto EG.
