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Ca2+/Mg2+ co-substituted strontium nanohexaferrites: magnetic investigation and Mossbauer analysis
(Springer, 2019) Almessiere, Munirah A.; Slimani, Yassine; Demir Korkmaz, Ayşe; Güngüneş, Hakan; Nawaz, Muhammad; Shirsath, Sagar E.; Ercan, İsmail
We report a comprehensive evaluation of the microstructures, magnetic, and hyperfine traits of Ca2+/Mg2+ co-substituted strontium nanohexaferrites (SHFs) of chemical compositions Sr1-2xCaxMgxFe12O19 (x <= 0.1). These SHFs were prepared using sol-gel unified auto-combustion strategy and characterized by diverse analytical measurements to determine the effects of Ca2+/Mg2+ co-substitution on the aforesaid properties. XRD and high resolution transmission electron microscpe (HRTEM) analyses confirmed the nucleation of HF nanocrystallites. UV-visible diffuse reflectance (DR-UV-Vis) spectra were used to evaluate the optical band gap of the proposed SHFs, which was reduced with the increase in co-substitution contents. The Fe-57 Mossbauer spectra was exploited to assess the quadrupole splitting, spectral line-width variation, isomer shift, distribution of cations (Ca2+ and Mg2+), and hyperfine magnetic fields. Measured magnetic parameters such as saturation magnetization, remanence, squareness ratio (SQR), coercivity, and magnetic moment were significantly improved due to the Ca2+/Mg2+ co-substitution. All the prepared SHFs revealed ferrimagnetic nature both at 10 and 300 K. Achieved SQR values approximate to 0.5 of the studied SHFs clearly disclosed their single domain character possessing uniaxial anisotropy. [GRAPHICS] .
Ca2+/Mg2+ co-substituted strontium nanohexaferrites: magnetic investigation and Mossbauer analysis (vol 93, pg 228, 2020)
(Springer, 2020) Almessiere, Munirah A.; Slimani, Yassine; Demir Korkmaz, Ayşe; Güngüneş, Hakan; Nawaz, Muhammad; Shirsath, Sagar E.; Ercan, İsmail
[Abstract Not Available]
Dielectric properties, cationic distribution calculation and hyperfine interactions of La3+ and Bi3+ doped strontium hexaferrites
(Elsevier Ltd, 2016) Auwal, İsmail A.; Ünal, Bayram; Güngüneş, Hakan; Shirsath, Sagar E.; Baykal, Abdulhadi
La3+ and Bi3+ doped M-type strontium hexaferrites (SrM) were prepared by sol–gel-auto combustion. X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), Vibrating Simple Magnetometer (VSM), Mössbauer Spectroscopy and Novo electrical conductivity system were used for structural, morphological, and electrical characterizations of the products. The cation distribution calculations of the products were also provided. Single-phase M-type SrM with a chemical composition SrFe12?2xLaxBixO19 (0.0?x?0.5) were confirmed by XRD analysis, which also provided lattice constants and crystallite sizes of each product. The crystallite size was in the range of 43–51 nm. SEM analysis confirmed the presence of hexagonal crystal formation while the EDX analysis confirmed the presence of metal ions in the required stoichiometric ratio. From 57Fe Mössbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting and hyperfine magnetic field values on Bi and La substitutions have been determined. It was observed that ac conductivity of SrM increases slightly with increasing La3+ and Bi3+ ion substitutions at first, and then fluctuates with further substitution. Moreover, ac conductivity also increased with increasing frequency which could be regarded as an indication of ionic conductivity. It can be noted that activation energy increases as the enhanced contributions of doped-ion substitutions in SrM NPs with the illustration of a better stability of electrical bonds among the substitutional ions and Fe ions.
Effect of bimetallic (Ni and Co) substitution on magnetic properties of MnFe2O4 nanoparticles
(Elsevier Ltd, 2016) Topkaya, Ramazan; Güngüneş, Hakan; Eryiğit, Ş. Ş.; Shirsath, Sagar E.; Yıldız, Aylin; Baykal, Abdulhadi
Nickel and cobalt substituted manganese ferrite nanoparticles (NPs) with the chemical composition NixCoxMn1–2xFe2O4 (0.0?x?0.5) NPs were synthesized by one-pot microwave combustion route. The effect of co-substitution (Ni, Co) on structural, morphological and magnetic properties of MnFe2O4 NPs was investigated using XRD, FT-IR, SEM, VSM and Mössbauer spectroscopic techniques. The cation distribution of all products were also calculated. Both XRD and FT-IR analyses confirmed the synthesis of single phase spinel cubic product for all the substitutions. Lattice constant decreases with the increase in concentration of both Co and Ni in the products. From 57Fe Mössbauer spectroscopy data, the variations in line width, isomer shift, quadrupole splitting and hyperfine magnetic field values with Mn2+, Ni2+ and Co2+ substitution have been determined. While the Mössbauer spectra collected at room temperature for the all samples are composed of magnetic sextets, the superparamagnetic doublet is also formed for MnFe2O4 and Ni0.2Co0.2Mn0.6Fe2O4 NPs. The magnetization and Mössbauer measurements verify that MnFe2O4 and Ni0.2Co0.2Mn0.6Fe2O4 NPs have superparamagnetic character. The saturation and remanence magnetizations, magnetic moment and coercive field were determined for all the samples. Room temperature VSM measurements reveals saturation magnetization value close to the bulk one. It has been observed that the saturation magnetization and coercive field increase with respect to the Ni and Co concentrations. © 2016 Elsevier Ltd and Techna Group S.r.l.
Electrical properties and hyperfine interactions of boron doped Fe3O4 nanoparticles
(Academic Press, 2015) Amir, Md.; Ünal, Bayram; Geleri, M.; Güngüneş, Hakan; Shirsath, Sagar E.; Baykal, Abdulhadi
The single spinel phase nano-structured particles of FeBxFe2-xO4 (x = 0.1, 0.2, 0.3, 0.4 and 0.5) were synthesized by the glycothermal method and the effect of B3+ substitution on structural and dielectric properties of Fe3O4 were studied. From 57Fe Mössbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting and hyperfine magnetic field values on B3+ substitution have been determined. The hyperfine field values at B- and A-sites gradually decrease with increasing B3+ ion concentration (x). The cation distributions obtained from Bertaut method are in line with Mössbauer results. Complex impedance analysis of boron-substituted spinel ferrites have been made extensively in order to investigate the significant changes in ac and dc conductivity as well as complex permittivity when the boron composition ratio varies from 0.1 to 0.5. It is found that both ac and dc conductivity are also dependent on the boron content in addition to both temperature and applied frequency. The dc conductivity tendency does not purely obey the Arrhenius plots. The dielectric constant and loss of complex permittivity, in general, show similar attitudes as seen in some nanocomposites containing spinel ferrites except for some fluctuations and shifts along the characteristics of the curves. Furthermore, their imaginary components of both permittivity and modulus are almost found to obey the power law with any exponent values varying between 0.5 and 2 in accordance with the level of boron concentrations. © 2015 Elsevier Ltd. All rights reserved.
Magnetic properties and cation distribution of bimetallic (Mn–Co) doped NiFe2O4 nanoparticles
(Springer New York LLC, 2017) Baykal, Abdulhadi; Eryiğit, Ş. Ş.; Amir, Md.; Güngüneş, Hakan; Sözeri, Hüseyin; Shirsath, Sagar E.; Sertkol, Murat; Asiri, Sarah Mousa
Nickel ferrite (NiFe2O4), an inverse spinel crystal structure and a soft transition metal oxide, contemplated as a good magnetic semiconducting material with low coercivity and saturation magnetization (M s). In this study, Ni1?2xMnxCoxFe2O4 (0.0???x???0.5) nanoparticles were synthesized by the microwave assisted approach with citric acid as fuel. The effect of both cobalt and manganese substitution on the morphological, structural, and magnetic properties of the NiFe2O4 nanoparticles were studied. X-ray powder diffraction patterns confirm their complete conversion to NiFe2O4 crystal phase and the increase in lattice constant provides evidence for the effect of both Co and Mn substitution. SEM images divulge the nano-size of the prepared products with speck morphology. Magnetic properties of the final products were evaluated using Vibrating Sample Magnetometer and 57Fe Mössbauer spectroscopy. The results from both analyses suggested the M s and coercive field of NiFe2O4 NPs increases as the concentration of Co and Mn increase and Ms getting closer to the bulk value.
Magnetic properties and hyperfine interactions of Co1-2xNixMnxFe2O4 nanoparticles
(Elsevier Ltd, 2017) Baykal, Abdulhadi; Eryiğit, Ş. Ş.; Topkaya, Ramazan; Güngüneş, Hakan; Amir, Md.; Yıldız, Aylin; Kurtan, Ümran; Shirsath, Sagar E.
Co1-2xNixMnxFe2O4 (0.0?x?0.5) nanoparticles (NPs) were prepared via citrate assisted microwave combus-tion route. XRD analysis confirmed the cubic structure (spinel) of all samples. Average crystallite size ofproducts (obtained from (311) diffraction line) was in the range of 32.9–43.4 nm. The intense peak appearing ataround 531 cm?1in FT-IR was attributed to the formation of a spinel ferrite. Magnetic properties of theproducts were investigated by room temperature vibrating sample magnetometer and Mössbauer spectroscopy.The magnetic parameters have been found to strongly depend on the Ni and Mn concentrations. The saturationmagnetization continuously decreases with the increasing of the concentration (x). We found thatNi0.5Mn0.5Fe2O4NP has superparamagnetic character at room temperature. This result was also verified byMössbauer analysis. Scanning electron microscopic analysis revealed the cubic morphology of all products, EDXand elemental mapping analyses confirmed the expected composition of each product.
Magnetic properties and Mössbauer spectroscopy of Cu-Mn substituted BaFe12O19 hexaferrites
(Elsevier Ltd, 2017) Baykal, Abdulhadi; Güngüneş, Hakan; Sözeri, Hüseyin; Amir, Md.; Auwal, İsmail A.; Asiri, Sarah Mousa; Shirsath, Sagar E.; Demir Korkmaz, Ayşe
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. © 2017 Elsevier Ltd and Techna Group S.r.l.
Magnetic properties of FeMnyCoyFe2?2yO4@Oleylamine nanocomposite with cation distribution
(Springer New York LLC, 2017) Amir, Md.; Demir Korkmaz, Ayşe; Baykal, Abdulhadi; Geleri, M.; Sözeri, Hüseyin; Güngüneş, Hakan; Sertkol, Murat; Shirsath, Sagar E.
In this study, oleylamine (OAm) capped FeMnyCoyFe2?2yO4 (0.0???y???0.4) nanocomposites (NCs) were prepared via the polyol route and the impact of bimetallic Co3+ and Mn3+ ions on the structural and magnetic properties of Fe3O4 was investigated. The complete characterization of FeMnyCoyFe2?2yO4@OAm NCs were done by different techniques such as XRD, SEM, TGA, FT-IR, TEM, and VSM. XRD analyses proved the successful formation of mono-phase MnFe2O4 spinel cubic products free from any impurity. The average crystallite sizes were calculated in the range of 9.4–26.4 nm using Sherrer’s formula. Both SEM and TEM results confirmed that products are nanoparticles like structures having spherical morphology with small agglomeration. Ms continued to decrease up to Co3+ and Mn3+ content of y?=?0.4. Although Mössbauer analysis reveals that the nanocomposites consist three magnetic sextets and superparamagnetic particles are also formed for Fe3O4, Co0.2Mn0.2Fe2.6O4 and Co0.4Mn0.4Fe2.2O4. Cation distributions calculation was reported that Co3+ ions prefer to replace Fe2+ ions on tetrahedral side up to all the concentration while Mn3+ ions prefer to replace Fe3+ ions on the octahedral.
Magneto-optical and microstructural properties of spinel cubic copper ferrites with Li-Al co-substitution
(Elsevier Ltd, 2018) Slimani, Yassine; Güngüneş, Hakan; Nawaz, Muhammad; Manikandan, A.; El Sayed, H. S.; Almessiere, Munirah Abdullah; Sözeri, Hüseyin; Shirsath, Sagar E.; Ercan, İsmail; Baykal, Abdulhadi
Nanospinel Li2xCu1-xAlyFe2-yO4 ferrites with composition x?=?y?=?0.0, 0.2, 0.3 and 0.4, were successfully synthesized via hydrothermal method. The effect of co-substitution (Li and Al) on structural, morphological and magnetic properties of CuFe2O4 nanoparticles were investigated using Powder X-ray Diffraction (XRD), Fourier-Transform Infrared spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Vibrating Sample Magnetometer (VSM) and Mossbauer spectroscopic techniques. The cation distribution of all composition was calculated. Both XRD and FT-IR analyses confirmed the synthesis of single-phase spinel cubic product for all the substitutions. Mossbauer investigation showed that the Li1+ and Al3+ ions occupied B-sites. Nonetheless, some amounts of Li1+ occupy A-site. The magnetization hysteresis loops M (H), revealed that the final products with x, y?=?0.0, 0.3 and 0.4 exhibit superparamagnetic (SPM) behavior at room temperature, however the composition x, y?=?0.2 displays a ferromagnetic-like (FM) behavior. The saturation magnetization (Ms) reduces with rising the Li and Al contents. Compared to pristine CuFe2O4 spinel, the remanent magnetization (Mr), coercive field (Hc) and the magneto-crystalline anisotropy fields (Ha) improved for products synthesized with x, y?=?0.2 and then decrease for x, y?=?0.3 and 0.4. The squareness ratio Mr/Ms are less than 0.500, which suggest the single domain nanoparticles with uniaxial anisotropy for Li2xCu1–xAlyFe2-yO4 (0.0?? x, y???0.4) nanoparticles. The magneto-crystalline anisotropy constant (Keff) value is improved for Li0.8Cu0.6Al0.2Fe1.8O4 (i.e. x, y?=?0.2) magnetic nanoparticles and then decreased for higher Li and Al contents, due to the replacement of Cu and Fe ions with respectively Li and Al ions.
Mössbauer analysis and cation distribution of Zn substituted BaFe12O19 hexaferrites
(Springer New York LLC, 2018) Auwal, İsmail A.; Demir Korkmaz, Ayşe; Amir, Md.; Asiri, Sarah Mousa; Baykal, Abdulhadi; Güngüneş, Hakan; Shirsath, Sagar E.
Barium hexaferrite is a well-known hard magnetic material. Doping using nonmagnetic cation such as Zn2+ were found to enhance magnetization owing to preferential tetrahedral site (4 f 1) 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 (Ba1?xZnxFe12O19) were synthesized by sol-gel method. In this study, we summarized the magnetic properties of Ba1?xZnxFe12O19 (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, 12k, 2a, and 4 f 2 positions which are close to theoretical values.
Oleylamine surface functionalized FeCoyFe2- yO4 (0.0?y?1.0) nanoparticles
(Elsevier B.V., 2016) Amir, M.; Baykal, Abdulhadi; Sözeri, Hüseyin; Güngüneş, Hakan; Shirsath, Sagar E.
In this study, oleylamine (OAm) capped FeCo y Fe2- y O4 (0.0?y?1.0) nanocomposites (NCs) were prepared via a polyol route. Effect of Co3+ ion substitution on structure, morphology and magnetic properties of Fe3O4 nanoparticles was investigated by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analyzer (TGA), scanning and transmission electron spectroscopy (SEM and TEM), vibrating sample magnetometer (VSM) and Mössbauer analyzer. All XRD patterns show the single phase spinel ferrite without any impurity. The crystallite size of the samples is within the range of 7.1-21.7nm. FT-IR analysis showed that all products were successfully packed by OAm. Both SEM and TEM results confirmed that products have spherical morphology with small agglomeration. When Co3+ ions were substituted to the Fe3O4, Ms continued to decrease up to Co3+ content of y =0.4. It was reported that Co3+ ions prefer to replace Fe2+ ions on octahedral side up to some concentration. Although the Mössbauer spectra for the all samples were composed of magnetic sextets, superparamagnetic particles are also formed for FeCo0.6Fe1.4O4, FeCo0.8Fe1.2O4 and FeCoFe2O4 samples. © 2016 King Saud University.
Structural investigation and hyperfine interactions of BaBixLaxFe12?2xO19 (0.0?x?0.5) hexaferrites
(Elsevier Ltd, 2016) Auwal, İsmail A.; Baykal, Abdulhadi; Güngüneş, Hakan; Shirsath, Sagar E.
Barium hexaferrite, BaFe12O19, substituted by Bi3+ and La3+ (BaBixLaxFe12?2xO19 where 0.0?x?0.5) were prepared by solid state synthesis route. The effect of substituted Bi3+ and La3+ ions on the structure, morphology, magnetic and cation distributions of barium hexaferrite were investigated by X-ray powder diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR) and Mössbauer spectroscopy. XRD powder patterns were refined by the Rietveld analysis method which confirmed the formation of single phase magneto-plumbite structure and the substitution of La3+ and Bi3+ ions into the lattice of barium ferrite. These results show that both La3+ and Bi3+ ions completely enter into barium hexaferrite lattice without disturbing the hexagonal ferrite structure. The EDX spectra confirmed the presence of all the constituents in expected elemental percentage. From 57Fe Mössbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting and hyperfine magnetic field values on Bi and La substitutions have been determined. Cation distribution in the presently investigated hexaferrite system was estimated using the relative area of Mössbauer spectroscopy.
Structural, magneto-optical properties and cation distribution of SrBixLaxYxFe12-3xO19 (0.0?x?0.33) hexaferrites
(Elsevier Ltd, 2016) Auwal, İsmail A.; Güngüneş, Hakan; Güner, Sadık; Shirsath, Sagar E.; Sertkol, Murat; Baykal, Abdulhadi
SrBixLaxYxFe12-3xO19 (00.0?x?0.33) hexaferrites were produced via sol-gel auto combustion. XRD patterns show that all the samples are single-phase M-type strontium hexaferrite (SrM). The magnetic hysteresis (?-H) loops revealed the ferromagnetic nature of nanoparticles (NPs). The coercive field decreases from 4740 Oe to 2720 Oe with increasing ion content. In particular, SrBixLaxYxFe12-3xO19 NPs with x = 0.0, 0.1, 0.2 have suitable magnetic characteristics (?s = 62.03-64.72 emu/g and Hc = 3105-4740 Oe) for magnetic recording. The intrinsic coercivity (Hci) above 15000 Oe reveals that all samples are magnetically hard materials. Tauc plots were used to specify the direct optical energy band gap (Eg) of NPs. The Eg values are between 1.76 eV and 1.85 eV. 57Fe Mössbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting, relative area and hyperfine magnetic field values on Bi3+ La3+ and Y3+ substitutions have been determined. © 2016 Elsevier Ltd. All rights reserved.
Structural, morphological, optical, cation distribution and Mössbauer analysis of Bi3+ substituted strontium hexaferrite
(Elsevier Ltd, 2016) Auwal, İsmail A.; Güngüneş, Hakan; Baykal, Abdulhadi; Güner, Sadık; Shirsath, Sagar E.; Sertkol, Murat
Single-phase M-type hexagonal ferrites, SrBixFe12?xO19 (0.0?x?1.0), were prepared by a co-precipitation assisted ceramic route. The influence of the Bi3+ substitution on the crystallization of ferrite phase has been examined using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and Mössbauer spectroscopy. The XRD data show that the nanoparticles crystallize in the single hexagonal magnetoplumbite phase with the crystallite size varying between 65 and 82 nm. A systematic change in the lattice constants, a=b and c, was observed because of the ionic radius of Bi3+ (1.17 Å) being larger than that of Fe3+ ion (0.64 Å). SEM analysis indicated the hexagonal shape morphology of products. From 57Fe Mössbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting and hyperfine magnetic field values on Bi substitutions have been determined.
Synthesis and characterization of Cu–Mn substituted SrFe12O19 hexaferrites
(Springer New York LLC, 2018) Amir, Md.; Baykal, Abdulhadi; Güngüneş, Hakan; Asiri, Sarah Mousa; Ercan, İsmail; Shirsath, Sagar E.
In this study, bimetallic (Cu–Mn) substituted SrFe12O19 hexaferrites [Sr1?2xMnxCuxFe12O19 (0.0???x???0.1)] were synthesized via sol–gel auto-combustion approach. The effect of bimetallic substitution on structure, morphology and magnetism of SrFe12O19 was investigated. SEM images divulge the nano-size of the prepared products with speck morphology. X-ray powder diffraction analysis affirmed their complete conversion to SrFe12O19 hexagonal crystal phase. The results from 57Fe Mössbauer suggested that all five important sextets of Sr1?2xMnxCuxFe12O19 hexaferrites effected due to the substitution of Cu and Mn ions. Cation distribution calculation showed that as the percentage of Mn and Cu increased in Sr1?2xMnxCuxFe12O19 (0.0???x???0.1), particularly for x?=?0.03 the relative area of 12k and 4f2 site increased. This indicates that Fe ions are migrated towards 12k and 4f2 octahedral site.
Synthesis and characterization of electrospun NiCoCdNdFeO4 nanofibers
(Elsevier B.V., 2020) Alahmari, Firas S.; Almessiere, Munirah Abdullah; Slimani, Yassine; Güngüneş, Hakan; Shirsath, Sagar E.; Akhter, Shameem; Baykal, Abdulhadi
We report here the production of novel Ni0.5Co0.5?xCdxNd0.02Fe1.78O4 nanofibers (NFs) (0.00 ? x ? 0.25) via electrospinning method with using polyvinylpyrrolidone (PVP) as a polymer agent. The investigation of the partial substitution effect of Co by Cd ions in Co0.5Ni0.5Fe1.78Nd0.02O4 NFs on their morphological, structural and magnetic properties was performed. The XRD confirmed the successful formation of Ni0.5Co0.5?xCdxNd0.02Fe1.78O4 (0.00 ? x ? 0.25) NFs with cubic structure. The hyperfine parameters were determined from the analysis of Mössbauer results. The hyperfine magnetic field of both sites was not much affected by the substitution. Mössbauer analysis indicated that the Cd2+ ions strongly occupy A site and the Fe3+ions emigrated from A site to B site, and hence the content of Co2+ions diminished at B site. Room temperature (RT; T = 300K) and 10 K magnetization curves were investigated via vibrating sample magnetometer (VSM). All prepared samples displayed ferrimagnetic behavior at both measured temperatures. The saturation magnetization (Ms) enhances from x = 0.00 to 0.05 and thereafter reduces with the further increase in Cd2+ ion contents. All the Cd-substituted samples displayed higher Ms values than that of the non-substituted sample. The improvement in Ms values with Cd substitution is largely ascribed to the surface spins effects and cations distribution on Td and Oh sites. Magnetic moments, remanence (Mr) and coercivity (Hc) were determined and investigated.
Synthesis and characterization of oleylamine capped MnxFe1-xFe2O4nanocomposite: Magneto-optical properties, cation distribution and hyperfine interactions
(Elsevier Ltd, 2016) Güner, Sadık; Baykal, Abdulhadi; Amir, Md.; Güngüneş, Hakan; Geleri, M.; Sözeri, Hüseyin; Shirsath, Sagar E.; Sertkol, Murat
Pure Fe3O4 NPs and Oleylamin (OAm) capped MnxFe1-xFe2O4 (MnxFe1-xFe2O4@OAm) (0.2 ? x ? 1.0) nanocomposites (NCs) were synthesized by the polyol route. Lattice parameter increases with increasing Mn2+ concentration, due to the respective larger ionic radius of Mn2+ ion compared with the Fe2+ ion. The VSM analyses revealed superparamagnetic characteristics of all samples. The extrapolated specific saturation magnetization (?s) values decreased from maximum 50.74 emu/g to minimum 15.34 emu/g by increasing Mn content. The particle size dependent Langevin function was applied to determine the magnetic particle dimensions (Dmag) between 9.10 nm and 21.50 nm. The observed magnetic moments of NPs and NCs are in range of (0.64–2.10) ?B and significantly less than 4 ?B of bulk Fe3O4. Magnetic anisotropy was determined as uniaxial and calculated effective anisotropy constants (Keff) are between 32.14 × 104 Erg/g and 8.71 × 104 Erg/g. The size dependent saturation magnetization suggests the existence of a magnetically dead layers around the magnetic cores for NCs between 0.72 nm and 1.29 nm. From 57Fe Mössbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting and hyperfine magnetic field values on Mn2+ substitution have been determined. Although, the Mössbauer spectra for the sample x = 0.2 is composed of ferromagnetic sextets, paramagnetic doublet is also formed for other samples. The percent diffuse reflectance spectroscopy (DR %) and Kubelka-Munk theory were used to specify the optical properties. The estimated optical band gap (Eg) values from Tauc plots are between 1.50 eV and 2.05 eV. Increasing Mn content in NCs increased the band gap at different magnitudes.
Synthesis and structural and magnetic characterization of BaZn x Fe12?x O19 hexaferrite: hyperfine interactions
(Springer New York LLC, 2017) Baykal, Abdulhadi; Sözeri, Hüseyin; Güngüneş, Hakan; Auwal, İsmail A.; Shirsath, Sagar E.; Sertkol, Murat; Amir, Md.
To study the effect of Zn substitution on structural magnetic properties and hyperfine interactions of barium hexaferrite, BaFe12?x Zn x O19 (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 Zn2+ as compared with Fe3+, 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 Zn2+ occupies 12k, 4 f 2, 4 f 1, and 2b sites and at the same time pushes Fe3+ ions towards 2a and 12 k 1 sites. From57Fe Mössbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting, and hyperfine magnetic field values on Zn2+ substitution have been determined.

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