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X-type samarium-cadmium co-substituted hexaferrite with compositions Ba 2-x Sm x Co 2 Cd y Fe 28-y O 46 (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 M S value varied from 67.01 Am2/kg to 50.43 Am2/kg; whereas the H c value changed from 2.95 kA/m to 6.17 kA/m, A high value of M S (67.01 Am2/kg) is observed in the pure sample, and a very low value of H c (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. [ABSTRACT FROM AUTHOR]

M-type, Ba 0.4 Pb 0.6 Fe 12- x Co x O 19 (x = 0.00, 0.10, 0.20, 0.30, 0.40) hexaferrites, synthesized using citrate gel auto combustion method, and heated at 950 °C, 4 h for lossless applications. XRD analysis shows the development of the M-phase, along with PbM and hematite. The microstructural analysis reveals the stacking clusters of hexagonally shaped platelets. TEM image and SAED pattern of x = 0.3 composition shows polycrystalline nature and formed particles observed to fused with neighbouring particles. M − H loops of all samples reveal hard magnetic behaviour and possess multi-domain structure. The maximum saturation magnetization of 55.427 A m2/kg is observed in x = 0.10 composition and coercivity of prepared hexaferrites was found to vary from 0.058 T to 0.390 T. The cobalt substitution has a strong influence on the dielectric properties of prepared hexaferrites. The value of ac conductivity increases with cobalt substitution from x = 0.00 to x = 0.10, and followed by a reduction from x = 0.10 to x = 0.40. The same trend is observed for the dielectric constant. The low value of loss tangent for all compositions shows apt scope for lossless application. [ABSTRACT FROM AUTHOR]

A series of Erbium substituted X-type Ba 2 Co 2 Er x Fe 28- x O 46 (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-Fe 2 O 3 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 (M S) is explained and supported by the Mössbauer spectroscopy. The maximum values of M S (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. [ABSTRACT FROM AUTHOR]

Polycrystalline nanoparticles of M-type Ca(ZrCo) x Fe 12−2 x O 19 (0.0 ≤  x  ≤ 1.0) hexaferrites were prepared using a simple heat treatment method at a low heating temperature of 650 °C. Effect of cobalt-zirconium substitution on the structural, microstructural, magnetic and dielectric properties was investigated. XRD analysis indicates that all the samples possess a hexagonal structure with anti-ferromagnetic α-Fe 2 O 3 phase. The values of lattice parameters and cell volume found to be increased with increasing the cobalt-zirconium substitution along with the amount of α-Fe 2 O 3 phase. Crystal symmetry has not affected by Zr–Co substitution in prepared calcium hexaferrite samples but the position of diffraction peak [108] is found to shift towards a lower angle as an increase in the substitution of Zr–Co. The crystallite size found to vary between 12 and 17 nm. SEM images show agglomerated grains and surface morphology has changed with Zr–Co substitution. EDX analysis of typical samples revealed the presence of Ca, Fe, Co, Zr. The magnetic analysis revealed the formation of multi-domain structure. Room temperature Mössbauer spectra of prepared samples show that all five sextets are merged together with a paramagnetic doublet and it confirmed that the size of particles is very small in the nano range. Single and double semicircle arcs were observed in Cole-Cole plots, due to the contributions of grain and grain boundaries resistance. [ABSTRACT FROM AUTHOR]

• SrFe 12 O 19 -/NiFe 2 O 4 nanocomposites with different weight ratios were synthesized in presence of crown flowers extract • FTIR and XRD analysis show the presence of M, S phases • The hexagonal platelet for M and spherical particles for S phase were observed • H C and M S decreased with increasing the spinel phase. • M;S- 9:1, 8:2, 7:3, 6:4 belong to a hard ferrite, and 5:5 shows soft magnetic nature. • M:S- 9:1 and 8:2 show weak exchange coupling interactions, whereas 7:3 and 6:4 depict partial exchange coupling interactions, and 5:5 composite possesses perfect exchange coupling interactions. [Display omitted] SrFe 12 O 19 (M-type hexaferrite) and NiFe 2 O 4 (spinel) nano ferrite powders were synthesized in the presence of Calotropis gigantea (crown) flowers extract separately. SrFe 12 O 19 /NiFe 2 O 4 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 SrFe 12 O 19 /NiFe 2 O 4 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. [ABSTRACT FROM AUTHOR]

M-type hexagonal ferrites with chemical composition Ba 0.5 Sr 0.5 Co x Al x Fe 12-2x O 19 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) have been synthesized using a standard ceramic method. The electromagnetic or microwave parameters have been measured in the frequency range of 8.2 to 12.4 GHz using a vector network analyzer. The microwave absorption or reflection loss (RL) of different compositions has been evaluated comprehensively as a function of frequency, thickness and substitution Co 2 + and Al 3 + ions. The frequency dependence of microwave absorption, accompanied by the observed RL peaks in compositions, is governed by the quarter wavelength and/or impedance matching mechanisms. It was observed that composition x = 0.2 possesses highest RL peak of − 40.4 and − 39.7 dB at 11.72 and 10.63 GHz with thickness of 1.4 and 1.5 mm respectively. It also exhibits − 10 dB wideband absorption bandwidth of 3.27 GHz at 1.5 mm and − 20 dB absorption bandwidth of 1.09 GHz at 1.4 mm. Composition x = 1.0 owes − 20 dB narrowband absorption bandwidth of 170 MHz at 1.7 mm. The microwave absorption can be tuned by varying frequency, thickness and substitution of Co 2 + and Al 3 + ions. The large RL suggests that the compositions could be a potential candidate for microwave absorbing materials. [ABSTRACT FROM AUTHOR]