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    AC susceptibility and hyperfine interactions of Mg-Ca ions co-substituted BaFe 12 O 19 nanohexaferrites
    (Elsevier Ltd, 2019) Almessiere, Munirah Abdullah; Slimani, Yassine; Güngüneş, Hakan; Ali, Sadaqat S.; Baykal, Abdulhadi; Ercan, İsmail
    Magnesium and calcium co-substituted Ba M-type nanohexaferrite (NHFs) is fabricated via sol-gel auto-combustion technique. The phase formation was proved by XRD powder pattern, FESEM and HR-TEM. Magnetic properties of Ba 1-2x Ca x Mg x Fe 12 O 19 (x ? 0.1) NHFs investigated by Mossbauer Spectroscopy. The variations in line width, quadrupole splitting, isomer shift, the cation distribution of Ca 2+ and Mg 2+ ions and hyperfine magnetic field values were estimated. The AC magnetic susceptibility and ZFC-FC measurements were also performed for the Ba 1-2x Ca x Mg x Fe 12 O 19 (x = 0.02 and 0.08) NHFs. The M FC -M ZFC results do not show blocking temperature peak, indicating the ferrimagnetic (FM) behavior of prepared products. Different models including Neel-Arhenius (N-A), Vogel-Fulcher (V-F) and critical slowing down (CSD) were tested to evaluate the AC-magnetic susceptibility behaviors. It is demonstrated that the magnetic interactions are important for x = 0.02 NHFs. © 2019
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    AC susceptibility and hyperfine interactions of vanadium substituted barium nanohexaferrites
    (Elsevier Ltd, 2018) Almessiere, Munirah Abdullah; Slimani, Yassine; Güngüneş, Hakan; El Sayed, H. S.; Baykal, Abdulhadi
    Vanadium ions substituted BaFe12O19 nanohexaferrites, BaFe12-xVxO19 (0.0??x???0.1), were produced through the sol-gel auto-combustion route. The structure, morphology and the elemental compositions of various products were examined using X–ray powder diffraction, scanning electron microscopy coupled with EDX and EDS elemental mapping. These techniques confirmed the formation of the desired Ba-nanohexaferrite phases. The crystallites size was found to be 55–58?nm range for all products. The magnetic properties of BaFe12-xVxO19 nanohexaferrites were investigated by Mossbauer spectroscopy, ZFC-FC magnetizations and AC susceptibility. The evolutions in the values of hyperfine magnetic field, isomer shift, quadrupole splitting, and line width were deduced via Mossbauer analysis. The experiments of ZFC and FC magnetizations indicated that no blocking temperature is observed in the temperature interval 2–400?K, which signals the typical ferromagnetic (FM) behavior for the produced nanohexaferrites. A super-spin glass like behavior is noticed at lower temperatures. The experiments AC susceptibility confirmed that the strength of magnetic interactions is enhanced for lower content of V3+ (x?=?0.02). For higher amount of V3+, the magnetic interactions are weakened. The obtained results are mainly accredited to the substitutions of Fe3+ ions by V3+ ions.
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    AC susceptibility and Mossbauer study of Ce3+ ion substituted SrFe12O19 nanohexaferrites
    (Elsevier Ltd, 2018) Almessiere, Munirah Abdullah; Slimani, Yassine; Güngüneş, Hakan; El Sayed, H. S.; Baykal, Abdulhadi
    Ce3+ ion substituted SrFe12O19, SrFe12-xCexO19 (0.0???x???0.5), nanohexaferrites were fabricated by citrate sol-gel combustion approach. X–ray diffractometry (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscope (EDX), EDX Elemental mapping, Fourier transform infrared spectroscopy (FT-IR) were used to study the structure and morphology of the samples. AC magnetic susceptibility and 57Fe Mossbauer spectroscopy have been operated to examine the hyperfine structure, static and dynamic magnetic properties. The values of variations in line width, quadrupole splitting, hyperfine magnetic field, and isomer shift have been estimated. The impact of Ce-ion substitution on AC magnetic susceptibility properties of Sr-hexaferrite were explored. The AC-susceptibility measurements reveal the frequency dependence of the magnetic responses, indicating strong magnetic interactions among the nanoparticles of the various products. In addition, it is determined that the magnetic interaction between the nanoparticles is weakened in the substituted products, due to the substitution of Fe3+ ions by Ce3+ ions.
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    Co-substitution of zirconium and neodymium on hyperfine interactions and AC susceptibility of SrFe12O19 nanohexaferrites
    (Chinese Society of Rare Earths, 2019) Almessiere, Munirah Abdullah; Slimani, Yassine; Güngüneş, Hakan; Baykal, Abdulhadi
    This study presents the influence of Zn and Nd co-substitution on structure, morphology, AC suscepti-bility and ZFC-FC magnetizations of Sr nanohexaferrites (NHFs), SrFe12x?Zn;Nd?xO19(0.0 x 1.0),which was produced by sol-gel approach. XRD powder patterns, scanning electron microscopy (SEM) andhigh-resolution transmission electron spectroscopy (HR-TEM) approve the synthesis of Sr M-type hex-aferrite. Mossbauer spectra show that Zn2?ions occupy 2b and 4f1sites while Nd3?ions locate at 2a,4f2and 12ksites. The magnetic properties of the produced Sr-NHFs were investigated also by ZFC-FCmagnetizations and AC susceptibility. According to theMFC-MZFCresults (between 2 and 400 K), noblocking temperature was detected which indicates the ferromagnetic (FM) behavior of NHFs. At lowertemperatures, a super-spin glass like behavior is discerned. The AC susceptibility indicates that themagnetic interactions are improved due to the inclusion of low content (x¼0.1) of Nd3?and Zn2?ionsinto the Sr-NHFs. However, with further increasing the Nd3?and Zn2?contents (x¼0.9), the magneticinteractions are weakened.
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    Correlation between chemical composition, electrical, magnetic and microwave properties in Dy-substituted Ni-Cu-Zn ferrites
    (Elsevier, 2021) Almessiere, Munirah Abdullah; Slimani, Yassine; Güngüneş, Hakan; Demir Korkmaz, Ayşe; Trukhanov, Sergei V.; Güner, Sadık; Baykal, Abdulhadi
    Dy3+ ion-substituted nanoferrites Ni0.4Cu0.2Zn0.4Fe2_ xDyxO4 (x <= 0.04) were produced via sol-gel method. Correlation between chemical composition, crystal structure, electrical, magnetic and microwave properties was investigated. All samples were characterized by single-phase state. It was observed that the increase of the Dy content leads to a decrease in the average crystallite size. The bandgap (Eg) was deduced to be between 1.83 and 1.86 eV. The measurements of magnetization versus applied magnetic field (M-H) and magnetization versus temperature (M-T) were investigated by vibrating sample magnetometer (VSM). Magnetic measurements revealed superparamagnetic character at room temperature. The magnetization was increased initially with doping Dy3+ in the ratio of x = 0.01 compering to the un-doped sample and thereafter dropped as Dy3+ ions content further increases. Microwave properties were discussed in terms of electromagnetic absorption in the frequency range 1-20 GHz. The occurrences of the intensive electromagnetic absorption in the frequency ranged from 1.6 to 2.7 GHz were observed. The changes in the amplitude-frequency characteristics correlated well with the level of chemical substitution (x) with Dy ions concentration.
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    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.
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    Effect of annealing temperature on magnetic and mössbauer properties of ZnFe2O4 nanoparticles by sol-gel approach
    (Springer New York LLC, 2018) Amir, Md.; Güngüneş, Hakan; Baykal, Abdulhadi; Almessiere, Munirah Abdullah; Sözeri, Hüseyin; Ercan, İsmail; Sertkol, Murat; Asiri, Sarah Mousa; Manikandan, A.
    In this study, spinel ZnFe 2 O 4 nanoparticles (NPs) were synthesized by citrate sol-gel route using nickel nitrates, ferric nitrates and citric acid by annealing at 900, 1000, and 1100 ? C. We reported the structural and magnetic properties (including Mössbauer analysis) for anisotropy ZnFe 2 O 4 NPs annealed at different temperatures. Fourier transform infrared (FT-IR) and X-ray powder diffraction (XRD) were utilized to analyze the structural properties of magnetic nanoparticles (MNPs). Morphological features of resultant MNPs were examined by scanning electron microscopy (SEM). The observed XRD results displayed that the crystallite size increased from 38.60 to 49.28 nm with increasing the annealing temperature in a distinct linear trend. The enhancement of saturation magnetization of the uniaxial ZnFe 2 O 4 NPs was studied and varied from 1.28 to 1.66 emu/g as the annealing temperature increases. The Mössbauer spectra results show that ZnFe 2 O 4 ferrites were paramagnetic in nature at room temperature (RT). © 2018, Springer Science+Business Media, LLC, part of Springer Nature.
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    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.
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    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.
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    Exploration of catalytic and cytotoxicity activities of CaxMgxNi1-2xFe2O4 nanoparticles
    (Elsevier Science Sa, 2019) Nawaz, Muhammad; Almessiere, Munirah Abdullah; Almofty, Sarah; Dönmez Güngüneş, Çiğdem; Slimani, Yassine; Baykal, Abdulhadi
    The CaxMgxNi1-2xFe2O4 (x <= 0.05) nanoparticles (NPs) have been synthesized hydrothermally. The XRD analyses confirmed the purity of all products and their spherical morphology and compositions were explained by SEM, TEM, EDX and Elemental mapping analyses. Results confirmed the composition of CaxMgxNi1-2xFe2O4. The surface area of them was determined by BET analysis. Results indicated that when x is increased surface area of CaxMgxNi1-2xFe2O4 is decreased as compare with x = 0.0, however, at high composition (x = 0.05), surface area is increased. Catalytic activity of CaxMgxNi1-2xFe2O4 (x <= 0.05) NPs was studied for the reduction of 4-nitrophenol as a model compound. Reaction was monitored by UV-spectrophotometer at room temperature and at different times. Among different compositions of CaxMgxNi1-2xFe2O4, it was noticed that x = 0.04 exhibited more activity for the reduction of 4-nitrophenol and x = 0.03 was observed least active. Results suggested that CaxMgxNi1-2xFe2O4 could be useful material for catalytic applications. Cytotoxicity activity of CaxMgxNi1-2xFe2O4 (x <= 0.05) NPs against HCT116 (Human colon cancer cell line) cell line and MCF-7 (breast cancer cell line) was evaluated by using MTT assay. It was observed that CaxMgxNi1-2xFe2O4 (x <= 0.05) NPs exhibited less cytotoxicity. Due to less cytotoxicity, CaxMgxNi1-2xFe2O4 may also be useful in the field of biomedical applications.
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    Hydrothermal synthesis of CoyZnyMn1-2yFe2O4 nanoferrites: Magneto-optical investigation
    (Elsevier Ltd, 2018) Asiri, Sarah Mousa; Sertkol, Murat; Güner, Sadık; Güngüneş, Hakan; Mujasam Batoo, Khalid; Saleh, Tawfik A.; Sözeri, Hüseyin; Almessiere, Munirah Abdullah; Manikandan, A.; Baykal, Abdulhadi
    Manganese ferrites nanoparticles (NPs) substituted with both Co2+ and Zn2+ simultaneously (CoyZnyMn1-2yFe2O4 NPs for y=0.0 to 0.5), have been produced by hydrothermal approach. The substitution with both Co2+ and Zn2+ ions on the structure, spectroscopic and magneto-optical properties of nanocrystalline MnFe2O4 spinel ferrites have been analyzed in detail. The formation of spinel phase and structural changes induced by Co2+ and Zn2+ ions substitutions were confirmed by X-ray diffraction studies. Rietveld refinement revealed the cubic spinel phase for all products (minor amount of Fe2O3). Lattice constant and crystallite size were found to decrease from 8.478 to 8.370 Å and from 14.68 to 8.22 nm, respectively with increasing substitution of Co2+ and Zn2+ ions. HR-SEM and HR-TEM micrographs revealed the high homogeneity cubic structure of samples. The hyperfine magnetic field values for all products after Mn2+, Zn2+ and Co2+ ions substitution were determined by Mössbauer analysis. The estimated optical Eg (Energy band gap) values are in the range of 1.41–1.54 eV for the samples. The smaller Eg values are mainly attributed to greater particle size and decreasing quantum confinement effect. © 2017 Elsevier Ltd and Techna Group S.r.l.
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    Impact of Eu3+ ion substitution on structural, magnetic and microwave traits of Ni-Cu-Zn spinel ferrites
    (Elsevier Sci Ltd, 2020) Almessiere, M. A.; Slimani, Yassine; Güngüneş, Hakan; Kostishyn, Vladimir G.; Trukhanov, Sergei; Trukhanov, Alex V.; Baykal, Abdulhadi
    Partially europium (Eu) substituted Ni0.4Cu0.2Zn0.4EuxFe2-xO4(0.0 <= x <= 0.10) nanostructured spinel ferrites (NSFs) were produced by sol-gel auto-combustion strategy. The XRD analyses verified the existence of the single-phase composition in all the investigated samples. The Mossbauer spectra were used to estimate the values of the line-width disparity, isomeric shift (IS), quadrupole splitting, and hyperfine magnetic field (HMF). The values of HMF of the A and B sites decreased with the rise in Eu substitutions. The paramagnetic contribution of the NSFs increased with the rise in Eu3+ contents. The S-parameters of the proposed NSFs were measured using co-axial method. The frequency dispersions of the permittivity and permeability were utilized to determine the reflection losses in the 1-20 GHz frequency range. The occurrences of the natural ferromagnetic resonance (NFMR) enabled substantial absorption of the electromagnetic energy ranged from 2.5 to 9.5 GHz. There was established a strong correlation between the level of chemical substitution (x) and amplitude-frequency characteristics of the studied spinel ferrites was established. Furthermore, the increase of Eu substitution strongly influenced the frequency characteristics of the NSFs. Anomalous changing of the resonant amplitude (more than 4 times) was shown. This can be explained by the appearance of indirect exchange interactions between Fe3+ (3 d(5)) and Eu3+ (4f(6)) electronic shells. Results revealed a potential for practical applications of such kinds of materials in functional radio electronic devices.
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    Impact of Gd substitution on the structure, hyperfine interactions, and magnetic properties of Sr hexaferrites
    (Elsevier Sci Ltd, 2021) Almessiere, Munirah Abdullah; Slimani, Yassine; Sertkol, Mehriye; Güngüneş, Hakan; Wudil, Yakubu Sani; Demir Korkmaz, Ayşe; Baykal, Abdulhadi
    Gd3+-substituted nano-sized Sr-hexaferrite, SrGd(x)Fe(12-x)O19 (0.00 <= x <= 0.05) NHFs (SrGd NHFs), were fabricated by a one-pot sol-gel combustion approach assisted by citric acid. The crystal structures, surface morphologies, magnetic properties, and hyperfine interactions of the calcined samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), high-resolution TEM (HR-TEM), vibrating sample magnetometry (VSM), and Mossbauer spectrometry. The oxidation states and chemical compositions of the NHFs were evaluated using XPS. The single-phase crystalline structures of all products were confirmed by XRD analysis. The average crystallite sizes determined from the peaks of the highest intensity using the Scherrer equation were between 38 and 50 nm. Using 57Fe Mossbauer spectroscopy data, the quadrupole splitting, hyperfine magnetic field, isomer shift, and line width variation of the products were determined. The Mossbauer spectra showed that octahedral (O-h) 12k and 2a sites were preferentially occupied by Gd3+ ions. The Gd3+ content was found to have no influence on the electron density around the Fe3+ ions at any crystallographic site. The magnetization (M) versus magnetic field (H) data were collected at room (300 K) and ultra-low (10 K) temperatures. Neither the zero-field cooling (ZFC) nor field cooling (FC) mode plots of magnetization vs. temperature revealed any blocking temperature peaks. Both the M H curves and FC-ZFC magnetization revealed ferrimagnetic behavior of the products. Furthermore, the FC-ZFC magnetization exhibited super-spin glass behavior at low temperatures. Reductions in the coercive field (H-c), saturation magnetization (M-s), and remanence (M-r) magnetization were achieved with Gd substitution of up to 0.03 into the hexaferrite system; however, with further increase in Gd content, these values started to increase. The calculated squareness ratio (M-r/M-s) revealed that all of the NHF samples were composed of single magnetic domain particles with uniaxial anisotropy.
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    Impact of La3+ and Y3+ ion substitutions on structural, magnetic and microwave properties of Ni0.3Cu0.3Zn0.4Fe2O4 nanospinel ferrites synthesized via sonochemical route
    (Royal Soc Chemistry, 2019) Almessiere, Munirah Abdullah; Slimani, Yassine; Demir Korkmaz, Ayşe; Baykal, Abdulhadi; Güngüneş, Hakan; Sözeri, Hüseyin; Manikandan, Ayyar
    In the current study, Ni0.4Cu0.2Zn0.4LaxYxFe2-xO4 (x = 0.00 - 0.10) nanospinel ferrites (NSFs) were fabricated via an ultrasonic irradiation route. The creation of single phase of spinel nanoferrites (NSFs) was investigated by X-ray powder diffractometry (XRD) and selected area diffraction pattern (SAED). The cubic morphology of all samples was confirmed by scanning and transmission electron microscopies (SEM and TEM) respectively. The UV-Vis investigations provided the direct optical energy band gap values in a narrow photon energy interval of 1.87-1.92 eV. The Fe-57 Mossbauer spectroscopy analysis explained that the hyperfine magnetic fields of Octahedral (Oh) and Tetrahedral (Td) sites decreased with substitution. The paramagnetic properties of NPs decrease with increase of content of doped ions. Investigations of magnetic properties reveal a superparamagnetic nature at 300 K and soft ferromagnetic trait at 10 K. The M-s (saturation magnetization) and M-r (remanence) decrease and the H-c (coercivity) increases slightly with La3+ and Y3+ substitution. The observed magnetic traits are deeply discussed in relation with the morphology, structure, magnetic moments and cation distributions. The microwave characterization of the prepared NSFs showed that, dissipation (i.e., absorption) of incoming microwave energy occurs at a single frequency, for each sample, lying between 7 and 10.5 GHz. The reflection losses (RL) at these frequencies range from -30 to -40 dB and the mechanism of which is explained in the framework of dipolar relaxation and spin rotation. The best microwave properties were obtained with a LaY concentration of x = 0.08 having an RL of -40 dB @ 10.5 GHz and an absorption bandwidth of 8.4 GHz @ -10 dB. With these high values of RL and absorbing bandwidth, LaY doped NiCuZn NSF products would be promising candidates for radar absorbing materials in the X-band.
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    Influence of Dy3+ Ions on the Microstructures and Magnetic, Electrical, and Microwave Properties of [Ni0.4Cu0.2Zn0.4](Fe2-xDyx)O-4 (0.00 <= x <= 0.04) Spinel Ferrites
    (Amer Chemical Soc, 2021) Almessiere, Munirah Abdullah; Slimani, Yassine; Güngüneş, Hakan; Demir Korkmaz, Ayşe; Zubar, Tatiana; Trukhanov, Sergei; Baykal, Abdulhadi
    [Ni0.4Cu0.2Zn0.4](Fe2-xDyx)O-4 spinel ferrite nanoparticles with different Dy3+ concentrations (0.00 <= x <= 0.04) were prepared by a citrate sol-gel auto-combustion technique. A strong correlation among Dy concentration, structural parameters, and magnetic, electrical, and microwave properties was established. An increase in the Dy3+ concentration is the reason for a rise in the crystal structure parameters (due to different ionic radii of Fe and Dy ions) and a slight increase in the average particle size with a minor reduction in the specific surface area. It was observed that Dy3+ ions prefer to occupy the octahedral B site due to their large ionic radius (0.91 A). The explanation of the electrical and magnetic properties was given in terms of the features of Dy3+-O2--Fe3+ dysprosium-oxygen-iron indirect exchange. The occurrence of the intensive changes in amplitude-frequency characteristics was observed from 1.6 to 2.7 GHz. The explanation of electromagnetic absorption was given in terms of the peculiarities of the microstructure (resonance of domain boundaries). The results open perspectives in the utilization of [Ni0.4Cu0.2Zn0.4](Fe2-xDyx)O-4 spinel ferrite nanoparticles as functional materials for targeted drug delivery and hyperthermia applications.
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    Investigation of the crystal/magnetic structure, magnetic and optical properties of SrYxNbxFe12-2xO19 (x <= 0.05) hexaferrites
    (Iop Publishing Ltd, 2020) Almessiere, Munirah Abdullah; Slimani, Yassine; Güngüneş, Hakan; Nawaz, Muhammad; Alahmari, Firas S.; Manikandan, Ayyar; Baykal, Abdulhadi
    Series of Sr hexaferrites (HFs) co-substituted with Nb3+ and Y3+ ions (SrYxNbxFe12-2xO19 (x <= 0.05) were prepared via sol-gel combustion method. In addition to their optical, low temperature, magnetic properties and hyperfine interactions were investigated in detail. X-ray diffraction (XRD) patterns were considered proving both the formation and pureness of products. Mossbauer analysis indicated that the hyperfine field on iron nuclei at all sites decrease with substitution of Y3+-Nb3+ ions into Sr-hexaferrite as a result of changing the magnetic Fe3+ (5 mu(B)) ions by nonmagnetic Y3+ and Nb3+ ions. This leads to decreasing of the magnetic super exchange interaction between the ions. Measurements of AC susceptibility and ZFC-FC magnetizations implemented in a range from room temperature (RT) down to around 2 K. The analysis of M-FC-M-ZFC data proves the ferrimagnetic performance of different prepared HFs in the whole range of 2-325 K and a super-spin glass-like behavior was identified at minimal temperatures. The investigation of AC susceptibility revealed a weakening in the magnetic exchange interactions with the rise in the Nb3+ and Y3+ ions ratios.
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    Investigation of the effects of Tm 3+ on the structural, microstructural, optical, and magnetic properties of Sr hexaferrites
    (Elsevier B.V., 2019) Almessiere, Munirah Abdullah; Slimani, Yassine; Güngüneş, Hakan; Manikandan, Ayyar; Baykal, Abdulhadi
    SrTm x Fe 12?x O 4 (0.00 ? x ? 0.10) hexaferrites (HFs) are produced successfully using a sol–gel approach. The structural, optical, and magnetic properties are investigated. The hexagonal phase is confirmed for all the products. The magnetization is measured with respect to the applied magnetic field, M(H). The magnetic parameters including saturation magnetization M s , remanence M r , squareness ratio (SQR = M r /M s ), coercivity H c , and magnetic moment n B are deduced at room (300 K; RT) and low (10 K) temperatures. It is shown that the ferrimagnetic nature and Tm 3+ substitutions lead to decreases in the magnetization and coercivity magnitudes. The results on magnetic properties are investigated extensively with respect to the structural and microstructural properties. The SQR values indicate the formation of a single magnetic domain for the x = 0.0 sample and a multi-magnetic domain structure for the Tm 3+ -substituted Sr HFs (x ? 0.02). The obtained H c values suggest that the produced HFs are promising candidates for potential magnetic recording applications. © 2019 The Authors
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    Magnetic and dielectric properties of Bi3+ substituted SrFe12O19 hexaferrite
    (Elsevier B.V., 2016) Auwal, İsmail A.; Erdemi, Hamit; Sözeri, Hüseyin; Güngüneş, Hakan; Baykal, Abdulhadi
    In the present study, SrBixFe12?xO19 (0.0?x?1.0) nanomaterials were successfully synthesized by using chemical co-precipitation method. Products were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Vibrating sample magnetometer (VSM), Mössbauer spectroscopy, AC conductivity and dielectric measurements. The crystal structural information studied by X-ray diffraction (XRD) indicated the formation of single phase pure hexagonal structure, while electron-dispersive X-ray spectroscopy (EDX) revealed the stoichiometric ratio among Bi, Sr, Fe elements. The crystallite sizes of the products were in the range of 65–82 nm. VSM analysis showed a tendency in saturation magnetization as Bi2O3 concentration raises, which can be ascribed to preferential site occupied by Bi3+ ions. The frequency-dependent ac conductivity plots exhibited similar trends for all samples. A significant temperature-dependent behavior was only observed at low and medium frequencies. The replacement of non-magnetic Bi3+ ions by Fe3+ ones having magnetic moment of 5 µB decrease the magnetic moment of 4f1 site. The AC conductivity increases with frequency as hopping of the charge carriers increases between Fe2+and Fe3+. The DC conductivity exhibited an improvement with increasing temperature and Bi content, and the highest conductivity was measured as 2.84×10?9 S cm?1 for x=0.8 at 120 °C. The variation of dielectric constant, dielectric loss and tangent loss was observed with the frequency and temperature due to change of electrical conductivity as x changes.
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    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.
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    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.