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Barium hexaferrite is a well-known hard magnetic material. Doping using nonmagnetic cation such as Zn were found to enhance magnetization owing to preferential tetrahedral site (4 f ) occupancy of the zinc. However, the distribution of cations in hexaferrites depends on many factors such as the method of preparation, nature of the cation, and chemical composition. Here, Zn-doped barium hexaferrites (BaZnFeO) were synthesized by sol-gel method. In this study, we summarized the magnetic properties of BaZnFeO ( x = 0, 0.1, 0.2, 0.3) BaM, investigated by Mössbauer spectroscopy. Moreover, cation distribution was also calculated for all the products. Mössbauer parameters were determined from 57Fe Mössbauer spectroscopy and according to it, the replacement of Ba-Zn affects all parameters such as isomer shift, the variation in line width, hyperfine magnetic field, and quadrupole splitting. Cation distribution revealed the relative area of undoped BaM, 12 k, 2 a, and 4 f positions which are close to theoretical values. [ABSTRACT FROM AUTHOR]

In this study, Y ion-substituted M-type barium hexaferrites (BaM; BaFeO) were fabricated via facile ceramic route. As-prepared powders were characterized by X-ray powder diffractometry (XRD), Fourier transform infrared (FT-IR) spectroscopy, and impedance spectroscopy. XRD (Rietveld) analyses confirmed the presence of a single characterization of all samples (except x = 0.0 and 0.1 samples). The crystallite sizes of products are found in the range of 47.2-63.2 nm. Spectral analysis (FT-IR) also presented the formation of spinel structure for all products. The ac conductivity of the substituted samples was found to initially decrease slightly with increase in Y compared with unsubstituted, and then variation tendency changes at the medium substitution ranges are observed with a different attitude against temperature. In the end, the lower conductivity for high substitutions is recorded and increases as functions of frequency while it also increases with the elevation of temperature. It was observed that ac conductivities of products increased by increasing frequency which indicate that observed ac conductivity is due to both electronic and polaron hopping mechanism. [ABSTRACT FROM AUTHOR]

BaLaBiFeO (0.0 ≤ x ≤ 0.5) hexaferrites were produced by solid-state synthesis route, and the effect of Bi and La substitutions on electrical and dielectric properties of barium hexaferrite material were investigated. It is noticed that ac conductivity of barium (BaM) increases slightly with ionic substitutions of both La and Bi and then decreases. Ac conductivity is increased with increasing frequency at lower temperatures then remains constant for higher temperatures. This type of conductivity attitude could be originated from the indication of both electronics and polaron hopping mechanisms. The dielectric properties of BaLaBiFeO (0.0 ≤ x ≤ 0.5) hexaferrites represent a very interesting tunability as functions of frequency, temperature, and Bi and La ions. [ABSTRACT FROM AUTHOR]

Yttrium doped barium hexaferrites with chemical composition BaY x Fe 12−x O 19 (0.0≤x≤1.0) were synthesized by facile ceramic route. The effect of the yttrium ion concentration on the temperature-dependent magnetic properties of the BaY x Fe 12−x O 19 hexaferrites (0.0≤x≤1.0) has been investigated in the temperature range of 10–300 K and magnetic field of 50 kOe. The structural, morphological, compositional and magnetic properties of the products were investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and vibrating sample magnetometer (VSM) techniques, respectively. XRD patterns demonstrated pure, single phase hexagonal crystal. The average crystallite size of the samples varies in the range of 47–63 nm. SEM images indicated hexagonal platelet-like particles. EDX measurements confirmed the expected formula of BaYFe 11 O 19 hexaferrite. It has been observed that the preferential site occupancy of the nonmagnetic yttrium ions strongly changes the magnetic properties. The saturation magnetization value close to the bulk one was measured as 62.62 and 88.21 emu/g for 300 and 10 K, respectively. It has been found from the magnetization measurements that the saturation magnetization reaches its maximum value at x=0.4 and then decreases with further increasing of the concentration (x). As the temperature goes up, the saturation magnetization decreases due to the weakening of superexchange interaction. The coercive field increases by about three times with increasing of the concentration from x=0.0 to 1.0 due to an increasing of anisotropy field and reaches the maximum value of 3556 Oe at x=1.0. [ABSTRACT FROM AUTHOR]

The Ho3+ ion-substituted SrBa nanohexaferrites, Sr0.5Ba0.5Fe12−xHoxO19 (x ≤ 0.1) (Ho → SrBa NHFs), were fabricated via ultrasonic-assisted sol–gel route. The hexagonal structure and plate-like morphology were confirmed by X-ray powder pattern (XRD), transmittance electron microscope (TEM), scanning electron microscope (SEM), and high-resolution transmittance electron microscope (HR-TEM). It has been found out that the crystallite size (DXRD) was within 45–74 nm range. Both elemental mapping and energy-dispersive X-ray spectroscopy (EDX) analyses provided the purity and expected chemical composition of the products. Using the M–H hysteresis loops (at 300 and 10 K), magnetic properties of Ho → SrBa NHFs are analyzed. Upon a sudden fall at x = 0.02, as soon as Ho ions are added, the magnetization is improved with the Ho substitution and prominently enhanced with decreasing temperature. However, the coercivity Hc is decreased with the Ho substitution. The Ho-doped samples represent a magnetically soft material at both high and low temperatures, which is also confirmed through M–T measurements. Their squareness ratio is found to be less than 0.5, suggesting the generation of multi-magnetic domains. The unsubstituted HFs and the samples with x = 0.02 and 0.06 show usual M–T variations with typical field-cooling (FC) and zero-field-cooling (ZFC) branches. However, the other samples (with x = 0.04, 0.08, and 0.10) exhibit unusual behavior with anomalies in their M–T plots. From 57Fe Mössbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting, and hyperfine magnetic field values on Ho3+ substitution have been determined. Mössbauer spectra show that Ho3+ ions located at generally octahedral 12 k site. The s-electron density of around Fe3+ ions has not influenced doped content. [ABSTRACT FROM AUTHOR]

Ni0.8Cu0.1Zn0.1MoxFe2–2xO4 (x ≤ 0.1) nanospinel ferrites (Mo → NiCuZn NSFs) were produced by sol–gel approach. A spinel structure formation with no impurities was confirmed by X-ray diffraction (XRD) patterns. The nanoparticles' morphology and chemical composition of the products have been confirmed via SEM, TEM, HR-TEM, and EDX. By fitting Mössbauer spectra at RT, Hyperfine parameters were determined. A superparamagnetic state was observed in all samples. The Mo4+ were found to reside in the B site mainly. Isomer shift values showed that Mössbauer spectra composed magnetic Fe3+ sextets. Magnetic characteristics of Mo → NiCuZn NSFs are probed employing hysteresis loops at 300 K and 10 K. The significant role of Mo ions in the magnetic characteristics of the host material is revealed by employing saturation magnetization (Ms), magnetic moment ( n B ), coercivity (Hc), SQR (squareness ratio), and magneto-crystalline anisotropy constant. While the samples show a superparamagnetic behavior at 300 K, they represent a magnetically soft material at 10 K. The magnetic parameters, with a minimum magnetization at x = 0.06, fluctuate with respect to Mo concentration at each temperature. The Ms and nB become the maximum for the Mo → NiCuZn NSFs (x = 0.02) which yields the minimum Hc. The SQR is negligible at 300 K and low (much less than 0.5) at 10 K, reflecting the generation of multi-magnetic domains and a relatively low anisotropy field. [ABSTRACT FROM AUTHOR]

In this study, bimetallic (Cu-Mn) substituted M-type Ba 1-2x Mn x Cu x Fe 12 O 19 (0.0 ≤ x ≤ 0.1) hexaferrites were fabricated via sol-gel auto-combustion route. The effect of bimetallic substitution on structure, morphology and magnetism of BaFe 12 O 19 was studied. Scanning Electron Microscopy confirm images reveal the nanosize of the prepared products with flake morphology. X-ray powder diffraction analysis confirmed their complete conversion to BaFe 12 O 19 hexagonal crystal phase. The results from the magnetic investigations conducted by Vibrating Sample Magnetometer (VSM) and 57 Fe Mössbauer suggested that the saturation magnetization ( M s ) and the coercive field of Ba 1-2x Mn x Cu x Fe 12 O 19 hexaferrites decrease as the concentration of Cu and Mn increases. The cation distribution calculation showed that the occupancy of Fe 3+ ions is increased at 12k and 2b sites with the increase in Cu and Mn substitution. [ABSTRACT FROM AUTHOR]

To study the effect of Zn substitution on structural magnetic properties and hyperfine interactions of barium hexaferrite, BaFeZnO (0.0≤ x≤0.3) hexaferrites were synthesized via sol-gel auto-combustion technique. Rietveld analysis of XRD powder patterns confirmed the formation of single-phase hexaferrites for all products. Due to the larger ionic size of Zn as compared with Fe, while x increases, the lattice constant parameters increase to a small degree. Nanoplate morphology of the products is presented by SEM analyses. It was observed that both saturation magnetization and coercivity decrease in almost the same manner with zinc concentration for all substitutions. Cation distribution calculations showed that Zn occupies 12 k, 4 f , 4 f , and 2 b sites and at the same time pushes Fe ions towards 2 a and 12 k sites. FromFe Mössbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting, and hyperfine magnetic field values on Zn substitution have been determined. [ABSTRACT FROM AUTHOR]

In this paper, the structural, morphological, electrical and dielectric properties of hard/soft ferrite nanocomposites (NCs) of CoFe 2 O 4 /(NiSc 0.03 Fe 1.97 O 4) x (where x = 1, 2, 3, 4, 5) have been investigated. The hard/soft NCs were manufactured with one pot sol-gel auto-combustion procedure. The electrical and dielectric properties of the products were explored with and between 20 and 120 °C temperature range up to 3 MHz. Dielectric and electrical features like ac/dc conductivity dielectric constant, dielectric loss and tangent loss were evaluated for a variety of compositional ratios of x = 1–5 including NiSc 0.03 Fe 1.97 O 4 and CoFe 2 O 4 NPs. The AC conductivity commonly obeys the power law rules, largely dependent on compositional ratios as mentioned earlier. Impedance analysis has the conduction mechanisms of hard/soft NCs at various compositional ratios are mainly due to grain-grain boundaries. The dielectric constant of the CoFe 2 O 4 and NiSc 0.03 Fe 1.97 O 4 NPs leads to normal dielectric distribution with frequency, largely dependent on compositional ratios. In general, the variation in the dielectric properties of hard/soft NCs caused by the conduction mechanism in ferrites. • Sol-gel auto-combustion procedure was employed to synthesize the hard/soft ferrites. • The AC conductivity generally largely dependent on compositional ratios. • Impedance analysis has observed that the conduction mechanisms of hard/soft NCs are mainly due to grain-grain boundaries. • The dielectric constant largely dependent on compositional ratios. [ABSTRACT FROM AUTHOR]