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The objective of this investigation is to study the structural and magnetic properties of Ni0.5Co0.5−xCdxFe2O4 (NCCFO) (x ≤ 0.20) nanofibers (NFs) fabricated utilizing the electrospinning technique. The phase purity and the chemical composition of the synthesized NFs were confirmed by PXRD and EDX via elemental mapping analysis. The magnetic properties for diverse NCCFO NFs were analyzed by measuring the magnetization as a function of magnetic field M(H). The synthesized NCCFO NFs are found to be ferrimagnetic, and referring to the pristine Ni0.5Co0.5Fe2O4 NFs, the saturation magnetization (Ms) value rises with rising Cd content. The greatest Ms of about 38.5 emu/g was obtained for x = 0.20 NFs. The enhancement of Ms throughout the NFs up to the maximum value of x was mainly attributed to the effects of surface spins, the cations distribution, the evolution of magneto-crystalline anisotropy, and the variation of magnetic moment (n B) . All prepared NFs displayed values of squareness ratio SR = M r / M s lower than 0.5, which indicates that these NFs consist of nanoparticles (NPs) with a single-magnetic domain (SMD) structure. Compared to the pristine Ni0.5Co0.5Fe2O4 NFs, the coercive field (Hc) was increased with rising Cd content up to x = 0.10. The largest Hc value belonging to x = 0.10 product is around 1005.7 Oe; then, Hc was decreasing with a further increase in the Cd content. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the optical, electric and dielectric properties of the Ni 0·5 Co 0.5-x Cd x Nd 0.02 Fe 1·78 O 4 (x ≤ 0.25) NFs prepared via electrospinning process. Diffuse reflectance spectroscopic (DRS) measurements were performed on pristine and all Cd-substituted NFs samples. Direct bandgap energies (E g) were extracted from the Tauc fits which were estimated in a range between 1.65 and 1.85eV. The electrical conduction mechanism and dielectric functions of Ni 0·5 Co 0.5-x Cd x Nd 0.02 Fe 1·78 O 4 NFs were comprehensively examined as functions of frequency, temperature and Cd ions substitution ratio in a 3D semi-logarithmic plot using the complex impedance spectroscopy technique. The substitution ratio has a robust influence on dielectric parameters including dielectric loss, dielectric constant, and dissipation factor while the Cd ion substitution has a weak effect on the conductivity mechanism. The activation energy values changed to a level lower than 400 meV with increasing the "x" values. [ABSTRACT FROM AUTHOR]

In this study, various Co 0.5 Ni 0.5 Bi x Fe 2-x O 4 (x ≤ 0.10) spinel ferrite nanofibers (CoNiBi SFNFs) have been synthesized by electrospinning technique. The structure, morphological, and magnetic features of CoNiBi SFNFs was investigated. XRD analysis demonstrated the formation of single-phase cubic spinel structure for all samples. The cell parameter is increasing with the increase of Bi3+ content. The cubic morphology of all products was also verified by SEM and TEM microscopies. Mössbauer analysis was used to determine the hyperfine parameters by fitting room temperature mosspectra. The Bi3+ ions occupy mainly the B site. Vibrating sample magnetometry (VSM) was applied to get magnetic data for CoNiBi SFNFs at 300 and 10 K. The characteristics of the recorded magnetic hysteresis curves revealed the existence of just ferrimagnetic phases for all fabricated spinel nanofiber samples at both temperatures. The remanent magnetization M r , saturation magnetization M S , magnetic moment per formula n B , coercivity H c have been determined. Bi3+ ion substitution commonly diminishes the magnetic data except the content of x = 0.04. The maximum and minimum magnitude of magnetic parameters belong to Co 0.5 Ni 0.5 Bi 0.04 Fe 1.96 O 4 and Co 0.5 Ni 0.5 Bi 0.10 Fe 1.90 O 4 SFNFs , respectively. Pristine Co 0.5 Ni 0.5 Fe 2 O 4 and Bi3+ ion doped samples exhibit soft magnetic at 300 K and hard magnetic nature at 10K conditions. Squareness ratio (SQR = M r /M s) provided extra information about the domain structure of fabricated nanofiber samples. At 10K conditions, SQR of the sample Co 0.5 Ni 0.5 Bi 0.04 Fe 1.96 O 4 is almost equal to 0.5 and this critical value is assigned to the formation of single domains with uniaxial symmetry for this nanofiber. This one only and all others have SQRs that are much lower (0.073–0.366) at 300K or higher (0.620–0.781) at 10K. Those ranges specify the multi-domain wall structure for samples. • Spinel ferrite nanofibers (CoNiBi SFNFs) have been synthesized by electrospinning technique. • Mössbauer spectra revealed the Bi3+ ions occupy mainly the B site. • The magnetization measurements at variable magnetic field (M − H) disclosed ferrimagnetic phases at 300 and 10 K. [ABSTRACT FROM AUTHOR]

• Nanostructured Dy-substituted Ni-Cu-Zn spinel ferrites were produced via sol-gel method. • Strong correlation between Dy concentration, magnetic and microwave properties was observed. • Control of the microwave properties can be used for functional radio electronics. Dy3+ ion-substituted nanoferrites Ni 0.4 Cu 0.2 Zn 0.4 Fe 2−x Dy x O 4 (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 (E g) 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. [ABSTRACT FROM AUTHOR]