Publications

X-type samarium-cadmium co-substituted hexaferrite with compositions Ba2-xSmxCo2CdyFe28-yO46 (0.00 ≤ x ≤ 0.08, and 0 ≤ y ≤ 0.4) were prepared at 1340 °C using a simple heat treatment technique. All heated samples were characterized using FTIR, XRD, SEM, VSM, Mӧssbauer, and low-frequency dielectric measurements. XRD analysis of prepared samples shows the formation of X as a major phase along with hematite. The MS value varied from 67.01 Am²/kg to 50.43 Am²/kg; whereas the Hc value changed from 2.95 kA/m to 6.17 kA/m, A high value of MS (67.01 Am²/kg) is observed in the pure sample, and a very low value of Hc (2.95 kA/m) is observed for x = 0.06, y = 0.3 compositions, but Mr/Ms < 0.5 confirm the multi-domain nature of prepared hexaferrites. Hysteresis loops of all samples are narrow, and confirmed that formed samples belong to magnetically soft. Mössbauer spectra of the three samples (S1, S3, and S5) show the existence of doublets. Significantly low values of coercivity, retentivity, and loss tangent in Sm–Cd substituted samples signified those prepared materials can be used to design electromagnets, transformer cores, electric motors, and maybe a potential candidate for lossless low-frequency applications.

A series of Erbium substituted X-type Ba2Co2ErxFe28-xO46 (x = 0.00, 0.04, 0.08, 0.12, 0.16, and 0.20) hexaferrites were prepared by the method of heat treatment. The obtained precursors were heated at 1350 °C for 6 h. XRD investigation reveals that x = 0.0 sample possesses X, W-type, and α-Fe2O3 phases, while Er- substituted samples show presence of X and W phases. The room temperature Mössabuer spectra have been fitted with five sextets. A variation in saturation magnetization (MS) is explained and supported by the Mössbauer spectroscopy. The maximum values of MS (52.29 Am²/kg) and anisotropy field-Ha (1370 kA/m) are found for x = 0.12 composition. Similarly, the maximum relative area (~69%) for spin up sites (k+a+b) is also found for x = 0.12 composition. Low frequency (20 Hz–2 MHz) dielectric response of all samples show normal behavior of ferromagnetic materials. The dielectric measurements reveal that the conduction in low frequency is due to grain boundary contributions and at the higher frequency it is due to grain contributions. AC conductivity is found to increase with frequency in all prepared hexaferrites. The substituted compositions can have potential applications in filter application due to soft ferrite behavior and low dielectric loss tangent.

SrFe12O19 (M-type hexaferrite) and NiFe2O4 (spinel) nano ferrite powders were synthesized in the presence of Calotropis gigantea (crown) flowers extract separately. SrFe12O19/NiFe2O4 nanocomposites were prepared in the presence of crown flowers extract and the effect of different weight ratios (M:S – 9:1, 8:2, 7:3, 6:4, 5:5) on structural, microstructural, magnetic, electrical transport, and dielectric properties were studied. The average crystallite size of nanocomposites was found from 25 nm to 44 nm. In addition, it was observed that the crystallite size of the M-phase decreased when the spinel phase increased. XRD analysis depicts the presence of both M and S phases in composites. The M-H loops analysis of SrFe12O19/NiFe2O4 composites indicates that the coercivity (3181–326 Oe), and saturation magnetization (57.5 Am²/kg. - 40 Am²/kg.) decreased when the spinel phase amount increased. Nanocomposites with weight ratios 9:1, 8:2, 7:3, 6:4 belong to a hard ferrite, while 5:5 shows soft magnetic nature. However, prepared composites possess a multi-domain structure. The weak exchange coupling interactions were found in composites 9:1 and 8:2, whereas the partial exchange coupling interactions were observed in composites 7:3, 6:4, and perfect exchange coupling interaction was noticed in 5:5.