Impact of La³⁺ and Y³⁺ ion substitutions on structural, magnetic and microwave properties of Ni<inf>0.3</inf>Cu<inf>0.3</inf>Zn<inf>0.4</inf>Fe<inf>2</inf>O<inf>4</inf> nanospinel ferrites synthesized: Via sonochemical route

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 Mössbauer 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

Effect of bimetallic (Ni and Co) substitution on magnetic properties of MnFe2O4 nanoparticles

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

Magnetic Attributes of NiFe2O4 Nanoparticles: Influence of Dysprosium Ions (Dy3+) Substitution

This paper reports the influence of dysprosium ion (Dy3+) substitution on the structural and magnetic properties of NiDyxFe2&minus;xO4 (0.0 &le; x &le; 0.1) nanoparticles (NPs) prepared using a hydrothermal method. The structure and morphology of the as-synthesized NPs were characterized via X-ray diffraction (XRD), scanning and transmission electron microscope (SEM, and TEM) analyses. 57Fe M&ouml;ssbauer spectra were recorded to determine the Dy3+ content dependent variation in the line width, isomer shift, quadrupole splitting, and hyperfine magnetic fields. Furthermore, the magnetic properties of the prepared NPs were also investigated by zero-field cooled (ZFC) and field cooled (FC) magnetizations and AC susceptibility measurements. The MZFC (T) results showed a blocking temperature (TB). Below TB, the products behave as ferromagnetic (FM) and act superparamagnetic (SPM) above TB. The MFC (T) curves indicated the existence of super-spin glass (SSG) behavior below Ts (spin-glass freezing temperature). The AC susceptibility measurements confirmed the existence of the two transition temperatures (i.e., TB and Ts). Numerous models, e.g., Neel&ndash;Arrhenius (N&ndash;A), Vogel&ndash;Fulcher (V&ndash;F), and critical slowing down (CSD), were used to investigate the dynamics of the systems. It was found that the Dy substitution enhanced the magnetic interactions

Magnetic Properties and Cation Distribution of Bimetallic (Mn-Co) Doped NiFe2O4 Nanoparticles

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 Fe-57 Mossbauer 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

Oleylamine surface functionalized FeCo Fe2−O4 (0.0 ⩽y⩽ 1.0) nanoparticles

In this study, oleylamine (OAm) capped FeCoyFe2-yO4 (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 Mossbauer analyzer. All XRD patterns show the single phase spinel ferrite without any impurity. The crystallite size of the samples is within the range of 7.1-21.7 nm. 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 Mossbauer 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. (C) 2016 Production and hosting by Elsevier B.V. on behalf of King Saud University