Static and high frequency magnetic and dielectric properties of ferrite-ferroelectric composite materials

Abstract

A series of sintered composite materials was fabricated from Parascan™ barium strontium titanate (BSTO) and Trans-Tech nickel zinc ferrite powders. The ferrite loading was varied from zero (BSTO only) to 100wt% (ferrite only). X-ray diffraction data show the presence of a third, nonmagnetic phase that sets the ferrite loading at values somewhat lower than the as prepared wt % amounts. The average magnetization is found to scale linearly with the loading. The initial susceptibility, saturation field, and coercive force as obtained from hysteresis loop data show trends consistent with these data. Ferromagnetic resonance linewidth and effective linewidth measurements at 10GHz show reasonable values for the 100wt% samples, but any amount of BSTO causes a severe degradation in both loss parameters. Similarly, it is found that any amount of ferrite causes a rapid drop in the relative dielectric constant that is consistent with standard mixing models. Loss tangent measurements gave modest values in the 0.001–0.005 range at 1MHz and much larger values in the 0.02–0.03 range at 10GHz.