Structural, magnetic and dielectric properties of Dy-Co substituted Sr-Ba-Mg-based magnetic oxides

In present research six samples of nano X-type hexagonal ferrites with general formula SrBaMg2-xCoxDyyFe28-yO46 (x = 0–1; y = 0–0.1 with step size of 0.2 and 0.02, respectively) were synthesized by sol–gel technique. The temperature required for the phase formation of these materials was estimated using thermogravimetric analysis. X-ray diffraction patterns revealed the pure phase of the prepared materials up to the doping concentration of x = 0.4, y = 0.04 along with the second phase for higher doping concentration. The secondary phase appeared due to the solubility limit of higher ionic radius Dy3+ ions into the hexagonal lattice. The mean crystalline size decreased from 29 to 18 nm while unit cell volume, bulk density, and X-ray density were increased with Dy-Co doping. Hysteresis loops showed that by incorporation of Dy-Co ions the saturation magnetization (Ms) was enhanced from 50 to 60 emu.g−1. Also, coercivity (Hc) varied in the range 1573–3251 Oe, such high values of Ms and Hc propose the utilization of these X-type materials as permanent magnets and perpendicular recording media. The dependence of dielectric parameters (dielectric constant, ac conductivity, Q-value) on frequency (1 MHz–3 GHz) as well as composition was discussed. Inclusion of Dy-Co in X-type lattice modified dielectric parameters i.e. dielectric constant, ac conductivity was increased. Complex modulus studies directed to elucidate Nyquist plots which exhibited a single half-circle for all X-type ferrites, thus depicting Debye sort of behavior.