Showing papers by "Sadik Güner published in 2019"

Microstructural, Optical, and Magnetic Properties of Vanadium-Substituted Nickel Spinel Nanoferrites

Abstract: The current study investigates the impact of vanadium substitution on the structural, magnetic, and optical properties of NiFe2−xVxO4 (x ≤ 0.3) nanoparticles (NPs) produced by the cost-effective sol-gel route. The as-prepared spinel ceramic powders were examined by X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy (DRS), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). The functional groups, spinel phase, and crystal structure were confirmed by XRD and FT-IR, respectively. The crystallites size decreased from 45.24 to 36.56 nm as the doping process increases. The plots of Tauc were drawn to determine optical band gap magnitudes of 1.291, 1.302, and 1.312 eV for x = 0.0, 0.2, and 0.3, respectively. The estimated saturation magnetization is maximum for pristine NiFe2O4 NPs and decreases to minimum for NiFe1.7V0.3O4 NPs. The σ-H hysteresis loops have finite coercivity (between 125 and 169 Oe) and retentivity (between 9.36 and 14.04 emu/g) values. The calculated σr/σs ratios are lower than 0.500, assigning the uniaxial anisotropy for NiFe2−xVxO4. The effective anisotropy constants (Keff) are in the range of 0.824 × 105 and 1.303 × 105 Erg/g. The magnetocrystalline anisotropy field (Ha) values are around 5.0 kOe. The characteristics of hysteresis (σ-H) curves and the order of magnetic data reveal the soft ferrimagnetic feature of as-prepared nanoparticle samples. From Mossbauer analysis, the variations in hyperfine magnetic field, quadrupole splitting, line width, and isomer shift have been evaluated. The distribution of cations showed that the octahedral B sites are occupied by all the ions of V3+. Mossbauer spectra are composed of four Zeeman sextets and one doublet.

Impact of La3+ and Y3+ ion substitutions on structural, magnetic and microwave properties of Ni0.3Cu0.3Zn0.4Fe2O4 nanospinel ferrites synthesized via sonochemical route

Abstract: 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 57Fe 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 Ms (saturation magnetization) and Mr (remanence) decrease and the Hc (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.

Calcination effect on the magneto-optical properties of vanadium substituted NiFe2O4 nanoferrites

Abstract: Vanadium substituted nickel ferrite nanoparticles (NPs), NiFe2−xVxO4 (0.0 ≤ x ≤ 0.3) were prepared by sol–gel approach. The influence of calcination on the magnetic and optical properties of NiFe2−xVxO4 (0.0 ≤ x ≤ 0.3) NPs were investigated deeply. The lattice parameters ‘a’ are almost constant with V-substitution for as-prepared and calcined samples. It was found that the calcination process both increased the crystallites size and removed the impurity phases in all products. The values of optical energy band gap, Eg, are in range of 1.38–1.69 eV and 1.39–1.56 eV for as-prepared and calcined samples, respectively. The specific magnetic parameters such as saturation magnetization Ms, remanence Mr, coercivity Hc, squareness ratio (SQR) and magnetic moment $$n_{B}$$ were determined from magnetization versus applied field measurements. The various M(H) curves exhibit ferromagnetic behavior at room temperature and 10 K. A decrease in Ms, Mr and $$n_{B}$$ values was observed with Vanadium substitution. However, an increase in Hc value was observed. The obtained magnetic results are primarily resulted from the substitution of Fe ions with V ions that will weaken the A–B super-exchange interactions. Besides, the calcination step leads to an improvement in the various Ms, Mr and $$n_{B}$$ parameters. This enhancement is due to the enlargement of crystallites size (or grains size) and the strengthening of the A–B exchange interactions caused by the calcination effect. Nevertheless, the enlargement in the crystallites size is followed by a reduction in Hc values.

Effect of Nb3+ ion substitution on the magnetic properties of SrFe12O19 hexaferrites

Abstract: The crystal structure and magnetic properties of SrNbxFe12–xO19 (0.00 ≤ x ≤ 0.08) nanohexaferrites (NHFs) fabricated using a sol–gel technique is presented in this study. The X-ray powder diffractometry (XRD) and Infrared spectroscopy (FT-IR) confirmed the formation of M-type hexaferrite phase. The analyses of magnetization versus applied magnetic field, M(H), were performed at room (300 K; RT) and low (10 K) temperatures. The Bohr magneton number (nB), saturation (Ms) and remanent (Mr) magnetization values increase slightly with increasing Nb3+ content. The room-temperature values of the magnetic parameters Mr = 31.41–33.28 emu/g, Ms = 57.10–60.14 emu/g and coercivity (Hc) between 4274 and 4540 Oe, at 10 K, magnetization data were detected that are much higher with respect to RT values: Mr = 45.96–51.06 emu/g, Ms = 94.42–95.99 emu/g. The magnetic results indicate that the samples are magnetically hard materials at both considered temperatures. The squareness ratio (SQR) is found to be around 0.50, implying single-domain NPs with uniaxial anisotropy for pristine and substituted samples. With exception, the x = 0.0 sample indicated the formation of multi-domain structure with uniaxial anisotropy at 10 K. Field cooling (FC) susceptibility measurements were applied in temperature range of 5–350 K for pristine sample and samples that contained some Nb3+ ions. The analyses of dc susceptibility data also proved that Nb3+ ion substitution increases the magnetization and, additionally, allows for an easier alignment of the magnetic domains. The obtained magnetic results were investigated deeply with relation to structural and microstructural properties. The observed remanent magnetization (Mr) and coercivity (Hc) render the products are useful for permanent magnets and high-density recording media.