Alterations in the magnetic and electrodynamic properties of hard-soft Sr0.5Ba0.5Eu0.01Fe12O19/NixCuyZnwFe2O4 nanocomposites

Hard/soft (H/S) Sr0.5Ba0.5Eu0.01Fe12O19/NixCuyZnwFe2O4 nanocomposites (NCs) were produced via a one-pot sol–gel auto-combustion procedure. Phase and surface analyses were performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HR-TEM). Magnetization measurements for H/S NCs with different x, y, and w ratios were investigated at two different temperatures (300 and 10 K). The M−H curves were not smooth for the different H/S NCs, revealing that the exchange interaction was incomplete. The derivative of the magnetization (dM/dH versus H) exhibited two separate peaks, confirming the non-coupled H/S mixtures. Maximum saturation magnetization (Ms) values of 93.9 and 63.1 emu/g were obtained at 10 and 300 K, respectively, for the H/S Sr0.5Ba0.5Eu0.01Fe11.99O19/Ni0.3Cu0.3Zn0.4Fe2O4 NC, which contained the highest content of Zn and the same contents of Ni and Cu within the soft magnetic phase. The calculated squareness ratios (SQR = Mr/Ms) were less than 0.5, indicating incomplete exchange coupling. The coercive field (Hc) of the produced NCs reached a maximum value of approximately 2485 Oe at 300 K and 2331 Oe at 10 K with a decrease in the Ms values to 56.9 emu/g at 300 K and 78.5 emu/g at 10 K for the H/S Sr0.5Ba0.5Eu0.01Fe11.99O19/Ni0.8Cu0.1Zn0.1Fe2O4 NC, which contained lower fractions of Zn and Cu and the highest fraction of Ni. The reflection/transmission-based waveguide approach was employed to investigate the electrodynamic properties of the H/S NC samples within a frequency band of 7–18 GHz. The reflection and transmission coefficients (S11/S21) were measured using a vector network analyzer (VNA) for the sample placed inside a waveguide. The frequency dispersions of the magnetic permeability and electric permittivity were calculated. © 2021 The Author(s)2020-164-IRMC; King Fahd University of Petroleum and Minerals, KFUPM; Russian Science Foundation, RSF: 21-79-10115This study was supported by the Deanship of Scientific Research of Imam Abdulrahman Bin Faisal University (Dammam, Saudi Arabia) through Grant No. 2020-164-IRMC . The authors also acknowledge support from the Center for Communication Systems and Sensing at KFUPM . Electromagnetic measurements and analysis were partially supported by the Russian Science Foundation (Agreement No. 21-79-10115)

An anthraquinone-functionalized reduced graphene oxide as electrode material for rechargeable batteries

The use of electro-active organic compounds as electrode materials in rechargeable batteries has been a very active research topic due to their high theoretical capacity, availability of various redox potentials depending on the electro-active group, ease of modification of properties, and improved safety. However, the issue of solubility in electrolytes limits their applications in batteries. The most common solutions for this problem involve incorporation of these organic molecules into the insoluble polymeric structures and trapping of these inside porous carbon materials. Here, we have demonstrated the covalent attachment of anthraquinone (AQ) derivatives via nitrene chemistry onto reduced graphene oxide (RGO) as another alternative. The successful synthesis of the RGO functionalized with anthraquinone groups (RGO-AQ), and its utilization as cathode materials in Li-batteries have also been demonstrated. The cells with RGO-AQ used as cathode materials initially discharged 126 mA h/g when cycled between 1.8 and 3.2 V at the rate of 5.35 mA/g in LiPF6/EC:DEC (1:1) electrolyte, and discharged 185.7 mA h/g when cycled between 13 and 3.6 V against Li metal at the rate of 6.0 mA/g in LiCIO4/PC electrolyte. (C) 2017 Elsevier Ltd. All rights reserved

Thermoelectric and Magnetic Properties of Pt-Substituted BaFe<inf>4</inf><inf>-</inf><inf>x</inf>Pt<inf>x</inf>Sb<inf>12</inf> Compounds

BaFe4-xPtxSb12 (x = 0, 0.1, 0.2) compounds were prepared by melting and annealing, followed by a spark plasma sintering method. Low-temperature thermoelectric and magnetic properties were investigated based on Seebeck coefficient, electrical and thermal conductivity and magnetization measurements. The structural properties of BaFe4-xPtxSb12 (x = 0, 0.1, 0.2) compounds were ascertained by powder x-ray diffraction analysis, confirming that all samples have a main phase of a skutterudite structure with the space group Im (3) over bar. The lattice parameters obtained, 9.202(5), 9.199(5) and 9.202(1) angstrom for x = 0, 0.1 and 0.2, respectively, were found consistent with literature. The Seebeck coefficient sign shows that holes are dominant carriers in all compounds. The local maximum Seebeck coefficient was observed around 50 K which may be a trace of paramagnon-drag effect of charge carriers. Thermal conductivity and electrical resistivity measurements were carried out between 4.2 K and 300 K. Temperature dependence of electrical resistivity reflects that all samples show semi-metallic behavior in our temperature range of 4.2-300 K. Samples for x = 0.1 and x = 0.2 show Kondo-like behavior. In magnetization measurement, we observe that there are two successive magnetic transitions in Pt-substituted compounds; however, there is only one (transition from a paramagnetic state to long-range magnetic ordering) in Pt-free compounds. In Pt-substituted compounds, the first transition appears at T-c = 48 K. In addition, the second transition is observed at T-irr = 30 K where an intermediate state is observed before the magnetic ordering transforms to an irreversible ferromagnetic state. We concluded that Pt substitution on the Fe side effectual on the thermoelectric and magnetic properties of BaFe4-xPtxSb12 (x = 0, 0.1, 0.2) compounds

Structural, optical and magnetic properties of Tb3+ substituted Co nanoferrites prepared via sonochemical approach

This paper emphasizes the structure, morphology, optical, and magnetic properties of sonochemically prepared terbium-substituted cobalt ferrite nanoparticles, CoTbxFe2-xO4 (0.00 ? x ? 0.10). The formation of cubic spinel nanosized ferrite structure was confirmed by X-ray diffraction (XRD), Field-emission scanning electron microscopy (FE-SEM), and Fourier-transform infrared (FT-IR) spectroscopy. The crystallites sizes were found in the range of 11–14 nm. Ultraviolet–visible percentage diffuse reflectance investigations were performed on pristine and Tb3+-doped cobalt spinel ferrite CoFe2O4 nanoparticles. The direct energy band gap (Eg) values were determined by applying the Kubelka–Munk theory and Tauc plots were found to be in a narrow band range of 1.37–1.44 eV. Analyses of magnetization versus the magnetic field (M(H)) were performed. The magnetic parameters, including the saturation magnetization (Ms), squareness ratio (SQR = Mr/Ms), magnetic moment (nB), remanence (Mr), and coercivity (Hc) were evaluated. The M(H) curves exhibited a soft ferrimagnetic nature. It was demonstrated that the Tb3+ substitutions strongly influenced the magnetization data. Indeed, the Ms, Mr, Hc, and nB values decreased with increasing Tb3+ substitution. © 2019 Elsevier Ltd and Techna Group S.r.l.Deanship of Scientific Research, King Saud University: 2018-209-IRMC, 2017-576-IRMCThis study was supported by the Deanship of Scientific Research (project applications 2017-576-IRMC and 2018-209-IRMC ) of Imam Abdulrahman Bin Faisal University (Saudi Arabia)

Structural, magnetic, optical properties and cation distribution of nanosized Ni0.3Cu0.3Zn0.4TmxFe2-xO4 (0.0???x???0.10) spinel ferrites synthesized by ultrasound irradiation

PubMedID: 31085087In this study, Tm3+ ion substituted NiCuZn nanospinel ferrites, Ni0.3Cu0.3Zn0.4TmxFe2-xO4 (0.0 ? x ? 0.10), have been synthesized sonochemically. The structural, spectroscopic, morphological, optic and magnetic investigation of the samples were done by X-ray powder diffractometry (XRD), Fourier transform infrared spectrophotometry (FT-IR), UV–Vis diffused reflectance (%DR) spectrophotometry, transmission and scanning electron microscopies (TEM and SEM) along with EDX, Vibrating sample magnetometry (VSM), respectively. The purity of prepared products were confirmed via XRD, FT-IR, EDX and elemental mapping analyses. The analyses of magnetization versus M(H) (applied magnetic field) were performed at 300 and 10 K. The following magnetic parameters like Ms (saturation magnetization), SQR = Mr/Ms (squareness ratio), nB(magnetic moment), Hc (coercivity) and Mr (remanence) have been discussed. M(H) loops revealed superparamagnetic property at RT and soft ferromagnetic nature at 10 K. It is showed that the Tm3+ substitutions significantly affect the magnetizations data. A decreasing trend in the Ms, Hc, Mr, and nB values was detected with Tm3+ substitution. © 2019 Elsevier B.V.2019-IRMC-S-1, 2017-IRMC-S-3, 2018-IRMC-S-2 Deanship of Scientific Research, King Faisal University: 2018-209-IRMC Islamic Azad UniversityThe authors appreciate the support of the Institute for Research & Medical Consultations (Projects No. 2019-IRMC-S-1, No. 2018-IRMC-S-2 and No. 2017-IRMC-S-3) and Deanship for Scientific Research (Project No. 2018-209-IRMC) of Imam Abdulrahman Bin Faisal University (IAU – Saudi Arabia)

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

The Effect of Cr3+ Substitution on Magnetic Properties of CoFe2O4 Nanoparticles Synthesized by Microwave Combustion Route

CoCr (x) Fe2-x O-4 (0.0 aecurrency sign x aecurrency sign 1.0) nanoparticles were synthesized by a microwave combustion method and the effect of Cr3+ substitution on structural, morphological, and magnetic properties of CoFe2O4 was studied. The structural, morphological, and magnetic properties of the products were determined and characterized in detail by X-ray diffraction (XRD), high-resolution scanning electron microscopy (HR-SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR), and vibrating sample magnetometer (VSM). Cation distribution of calculations confirmed the B site (octahedral site) preference of substituted Cr3+ ions. X-ray analysis showed that all compositions crystallize with a cubic spinel-type structure. The lattice parameter decreased from 8.384 to 8.362 with increasing Cr content. The average crystallite size was found in the range of 30.6-45.4 nm. Magnetization measurements showed that saturation magnetization of products decreases with the increase of the Cr substitution (x).Fatih University under BAPFatih University [P50031504_B]This study is supported by the Fatih University under BAP grant no. P50031504_B

Sonochemical Synthesis of CoFe2-xNdxO4 Nanoparticles: Structural, Optical, and Magnetic Investigation

This investigation deals with CoFe2-xNdxO4 (x ? 0.2) nanoparticles (NPs) fabricated by sonochemically. The purity of all products was verified via X-ray powder diffraction. The crystallite size of the samples was calculated as less 12 nm. The spectral analyses also confirmed the presence of spinel ferrites. Both morphology and chemical purity of the spinel ferrite systems were confirmed by SEM, EDX, and elemental mapping analyses. The analyses of magnetization versus applied magnetic field, M(H), were performed. The following magnetic parameters like saturation magnetization Ms, squareness ratio (SQR = Mr / Ms), magnetic moment nB, coercivity Hc, and remanence Mr have been evaluated. The M(H) curves revealed the soft ferromagnetic nature for all CoFe2-xNdxO4 NPs. It is showed that the Nd3+ substitutions significantly affect the magnetization data. A decreasing trend in the Hc, Ms, nB, and Mr values was detected with Nd3+ substitution. © 2019, Springer Science+Business Media, LLC, part of Springer Nature

Electrical and Dielectric Properties of Y3+-Substituted Barium Hexaferrites

In this study, Y3+ ion-substituted M-type barium hexaferrites (BaM; BaFe12O19) were fabricated via facile ceramic route. As-prepared powders were characterized by X-ray powder diffractometry (XRD), Fourier transform infrared (FT-IR) spectroscopy, and impedance spectroscopy. XRD (Rietveld) analyses confirmed the presence of a single characterization of all samples (except x = 0.0 and 0.1 samples). The crystallite sizes of products are found in the range of 47.2-63.2 nm. Spectral analysis (FT-IR) also presented the formation of spinel structure for all products. The ac conductivity of the substituted samples was found to initially decrease slightly with increase in Y3+ compared with unsubstituted, and then variation tendency changes at the medium substitution ranges are observed with a different attitude against temperature. In the end, the lower conductivity for high substitutions is recorded and increases as functions of frequency while it also increases with the elevation of temperature. It was observed that ac conductivities of products increased by increasing frequency which indicate that observed ac conductivity is due to both electronic and polaron hopping mechanism