Showing papers in "Journal of Superconductivity and Novel Magnetism in 2021"

First-Principles Calculations to Investigate Structural, Electronic, Elastic, Magnetic, and Thermodynamic Properties of Full-Heusler Rh 2 MnZ (Z = Zr, Hf)

Abstract: The structural, electronic, elastic, magnetic, and thermodynamic properties of two new Heusler alloys Rh2MnZ (Z = Zr, Hf) are studied based on the first principal calculation using the scheme of the generalized gradient approximation (GGA) of density function theory. The investigation was carried out in ferromagnetic (FM), anti-ferromagnetic (AFM), and the non-magnetic (NM) phases of the Cu2MnAl-type structure (regular structure) and Hg2CuTi-type-structure (inverse structure). Both alloys were found to be more stable in the ferromagnetic phase of the Cu2MnAl-type structure. The equilibrium lattice parameter in this structure is equal to 6.39 Ǻ for Rh2MnZr and 6.35 Ǻ for Rh2MnHf. The electronic properties reveled the metallic nature of the Heusler Rh2MnZ (Z = Zr, Hf) alloys. The interpretation of the elastic properties confirmed the elastic stability of the two alloys in the studied structure with a good agreement between the resulting bulk modulus from the structural properties and that of resulting from the elastic properties. Other elastic parameters such as modulus B, shear modulus G, Young’s modulus E, Poisson’s ratio (ν) and Pugh’s ratio B/G, and the Zener anisotropy parameter A showed that the Rh2MnZ (Z = Zr, Hf) alloys are slightly deformed. They show high rigidity, anisotropic, and little deformation and behave in ductile way. The magnetic properties confirmed the ferromagnetic state of both compounds with computed total magnetic moment equal to 4.76 μB for Rh2MnZr and 4.60 μB for Rh2MnHf. The thermodynamic parameters were evaluated with various temperatures between 0 and 1200 K and a pressure from 0 to 50 GPa using the quasi-harmonic Debye model.

Magnetic Nanoparticles in Targeted Drug Delivery: a Review

Abstract: Magnetic nanoparticles are one of the most important and widely used types of nanomaterials, whose unique properties make them special compared to other nanostructures. These particles can be used in various fields. But their role in biomedicine, especially in the field of drug delivery, is significant because their inherent magnetism facilitates many tasks, including targeting, which is very important and necessary in drug delivery. In the present article, an attempt has been made to give general information about magnetic nanoparticles and the properties of particles in biomedical applications. In the following, special attention has been paid to the properties of these particles in drug delivery and their various applications have been studied. The importance of coating magnetic nanoparticles has also been mentioned as a basic requirement for medical applications. In the following, the method of drug loading in magnetic nanoparticles, the entry of particles into the body, targeting, and drug release are discussed, and finally, a brief discussion is presented regarding the pharmacokinetics of drugs and their toxicity in the body.

Review on Recent Advances of Synthesis, Magnetic Properties, and Water Treatment Applications of Cobalt Ferrite Nanoparticles and Nanocomposites

Abstract: Nowadays, CoFe2O4 (cobalt ferrite) nanoparticles have fascinated numerous researcher’s consideration because of their latent implementation in water treatment. CoFe2O4 nanoparticles are cost-efficient magnetic materials and are stable under diverse environments. Therefore, they are effortlessly removed from purified water by means of an external magnetic field and reclaimed for quite a lot of cycles. In this analysis, the focus was given on learning the influences of some aspects including calcination temperature, crystalline size, pH, synthesis method, and dopant type on the magnetic properties of CoFe2O4 nanocomposites and nanoparticles. The implementation of CoFe2O4 nanoparticles in water purification and its capability to be united with various nanoparticles for adsorption and photocatalysis were entirely conferred. The chance of retrieval and reprocess of CoFe2O4 nanoparticles and its nanocomposites were discussed. Finally, the holes which are still not built up for study in the modification of physical properties and further magnetic properties of CoFe2O4 nanoparticles for its complete usage in water treatment were delineated. Henceforth, using CoFe2O4 nanoparticles and its nanocomposites at trade scale for water treatment will definitely reduce the expenses of water as it uses visible light as the energy source and because of its capability to be recycled numerous times.

Machine Learning F-Doped Bi(Pb)–Sr–Ca–Cu–O Superconducting Transition Temperature

Abstract: The increase in critical temperature of high-temperature superconductors fulfills needs of practical applications with liquid-helium-free refrigeration and a delay in magnet failure. But the research requires significant manpower for materials synthesis, characterization, and quench detection, as well as costly equipment and facilities. In this study, we develop the Gaussian process regression (GPR) model to shed light on the relationship between process parameters and superconducting transition temperature for BiPbSrCaCuOF superconductors. The modeling approach has a high degree of accuracy and stability, contributing to fast low-cost estimations of superconducting transition temperature.

Impact of Lanthanum-Doping on the Physical and Electrical Properties of Cobalt Ferrites

Abstract: Cobalt ferrites have attracted extraordinary attention due to their high coercivity, chemical stability, and mechanical hardness. Lanthanum doped-cobalt ferrites having chemical formula CoLaxFe2-xO4 with composition x = (0.00, 0.015, 0.045, 0.060) were synthesized by chemical co-precipitation method. The prepared samples were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and current-voltage (I-V) technique. The structure of the crystal was analyzed by X-ray diffraction. The crystallite size of nanoparticles was examined in the range of 21–25 nm, and a fluctuating trend was found with the inclusion of La3+ cations. The X-ray diffraction patterns verify the contraction of lattice constant and unit cell volume with the substitution of La3+ cations except for the concentration of x = 0.060. Lattice constant was in the range of 8.34 A–8.41 A while unit volume cell was in the range of 580 A3–596 A3. The resistivity of all samples was calculated by the application of two probes I-V technique. The maximum resistivity of the order of 81.129 × 105 Ω cm was found for the concentration of x = 0.060 at 723 K which makes it useful for high-frequency gimmicks applications. The resistivity and drift mobility were found inversely related to each other. The inverse relation low-frequency absorption band and high-frequency absorption bands were analyzed by Fourier-transform infrared spectroscopy technique.

Magnetic Hyperthermia and Photocatalytic Properties of MnFe2O4 Nanoparticles Synthesized by Solvothermal Reflux Method

Abstract: Development of new superparamagnetic materials with narrow size distribution is crucial for biomedical and environmental applications. Hence, we report the synthesis of narrow size distributed single grain MnFe2O4 nanoparticles of average particle size 9 nm by solvothermal reflux method. Synthesized compound crystallized in face centered cubic spinel structure and is confirmed by X-ray diffraction profiles. Transmission electron micrograph shows narrow size distributed particles with an average particle size of 9 nm and is equal to crystallite diameter estimated from Scherrer equation. The spinel crystal structure is further confirmed by electron diffraction profiles, Fourier transformed infrared spectrum, and Raman spectrum at room temperature. Magnetic properties of the sample show superparamagnetic nature at room temperature with moderate saturated magnetization of 56.4 emug−1. Magnetic heating properties of nanoparticles dispersion show the attainment of hyperthermia temperature (43 °C) in a short span of time of 1.6 min for 2 mg/mL and 2.6 min for 1 mg/mL concentrations. Estimated specific heat generation rate or specific power absorption rate, from temporal temperature plots, is 145.78 Wg−1 and is useful for magnetic hyperthermia application in cancer therapy. Photocatalysis properties of sample show 96% of rhodamine B dye degradation in little less than 6 h under UV light irradiation and are useful for photocatalytic applications in wastewater treatment in industries.

Effect of Barium Hexaferrites and Thermally Reduced Graphene Oxide on EMI Shielding Properties in Polymer Composites

Abstract: Barium hexaferrites (BaFe) and thermally reduced graphene oxide (TRGO) were successfully prepared by co-precipitation and improved hummer’s method, respectively. Nanocomposite films based on the thermoplastic polyurethane (TPU) matrix with different compositions of TRGO and BaFe were prepared by a solution casting method with a thickness of 0.25 mm. Electromagnetic interference (EMI) shielding is the key application area of these nanocomposites in the microwave frequency range of 0.1–20GHz and near infrared (NIR) wavelength range of 700–2500 nm. A maximum of 3.5*10−5 S/cm AC conductivity and 4.8*10−6 S/cm DC conductivity was achieved. The dielectric constant and dielectric loss also enhanced 2–3 times with respect to the pure TPU matrix. Less than 0.5% transmission in the NIR region and −40 dB shielding were observed in the microwave region. The highest shielding of −61 dB was achieved at frequency 12.5GHz.

M-Type Barium Hexaferrite-Based Nanocomposites for EMI Shielding Application: a Review

Abstract: The electromagnetic radiation emission at high radio frequency causes electromagnetic interference (EMI) which is a serious issue EMI shielding materials are necessary to shield the incoming electromagnetic waves to prevent this problem Hence, the advancement of high-performance EMI absorbers with flexibility, strong absorption, and extensive bandwidth has gained great attention Recently, M-type barium hexaferrite as EM interference absorber has gained much interest, owing to their high magnetic loss, high saturation magnetization, flexibility, low cost, high Curie temperature, and strong absorption Furthermore, due to high density, the incorporation of other dielectric loss fillers such as conductive polymers, graphene, and carbon nanotubes are studied as an essential way to improve the microwave’s absorption In this review, we present the EMI theory and also summarize modern improvements in the fabrication of barium hexaferrite-based materials comprising substituted barium ferrite and chemical integrations with conductive polymers, graphene, CNTs, and multicomponent composites The key points of increasing the EMI absorption in barium hexaferrite-based materials are to regulate the EM properties, improving the impedance match, and expanded the loss mechanisms

Symmetry Properties of Superconducting Order Parameter in Sr2RuO4: A Brief Review

Abstract: Soon after the discovery of superconductivity in Sr2RuO4 (SRO) a quarter-century ago, it was conjectured that its order parameter (OP) has a form similar to that realized in the superfluid phases of 3-He, namely, odd parity and spin triplet. While the chiral p-wave pairing believed to be realized in the A phase of that system was favored by several early experiments, in particular, the muon spin rotation and the Knight shift measurements published in 1998, the original Knight shift result was called into question in early 2019, raising the question as to whether the “chiral p-wave”, or even the spin-triplet pairing itself, is indeed realized in SRO. In this brief pedagogical review, we will address this question by counterposing the currently accepted results of Knight shift, polarized neutron scattering, spin counterflow half-quantum vortex (HQV), and Josephson experiments, which probe the spin and orbital parts of the OP, respectively, with predictions made both by standard BCS theory and by more general arguments based only on (1) the symmetry of the Hamiltonian including the spin-orbital terms, (2) thermodynamics, and (3) the qualitative experimental features of the material. In the hope of enhancing readers’ intuitive grasp of these arguments, we introduce a notation for triplet states alternative to the more popular “d-vector” one which we believe well suited to SRO. We conclude that the most recent Knight shift and polarized neutron scattering experiments do not exclude in the bulk the odd-parity, spin-triplet “helical” states allowed by the symmetry group of SRO but do exclude the “chiral p-wave”, ${{{\varGamma }}}_{5}^{-}$ state. On the other hand, the Josephson and in-plane-magnetic-field stabilized HQV experiments showed that the pairing symmetry in SRO cannot be of the even-parity, spin-singlet type, and furthermore, that in the surface region or in samples of mesoscopic size the d-vector must be along the c axis, thus excluding all bulk p-wave states except ${{{\varGamma }}}_{5}^{-}$ . Possible resolution of this rather glaring prima facie contradiction is discussed, taking into account implications of other important experiments on SRO, including that of the muon spin rotation, which are touched upon briefly only towards the end of this article.

A First-Principles Investigation on Electronic Structure, Optical and Thermoelectric Properties of Janus In2SeTe Monolayer

Abstract: The Janus two-dimensional (2D) materials have recently demonstrated excellent physical and chemical properties. The electronic, thermoelectric, and optical properties of the Janus In2SeTe monolayer have been investigated using density functional theory (DFT) calculations. Our results revealed the Janus In2SeTe monolayer has a direct bandgap of 1.07 eV, which is desirable and smaller than that of InSe and InTe. The studied optical properties indicate that Janus In2SeTe monolayer has a very good absorbing capability of light from the infrared region to ultraviolet one with a large absorption coefficient. Moreover, the thermoelectric property calculations suggest that the In2SeTe Janus monolayer can be a potential thermoelectric material, with a great electronic figure of merit ( $${ZT}_{\mathrm{e}}$$ ) of 0.97 at 300 K. In addition, the $${ZT}_{\mathrm{e}}$$ increases with temperature up to a value of 1.42 at 800 K. Our results revealed the Janus In2SeTe monolayer possesses good properties that could offer the possibility of optoelectronic and energy conversion applications.

Microstructural, Optical and Magnetic Study of Ni–Zn Nanoferrites

Abstract: NixZn1-xFe2O4 (x = 0.0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1.0) nanoferrites were synthesized using the citrate precursor method with high-purity metal nitrates and citric acid as synthesis precursors. For a detailed analysis of the structural, optical and magnetic properties of these nanoferrites sintered at 700 °C for 3 h, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and vibrating sample magnetometer (VSM) tests were done. The analysis of XRD patterns of the powdered samples revealed that the nanoferrites have a spinel structure, and the crystallite size of the nanoferrites ranged from 23 to 31 nm. The nanoferrite samples were found with a maximum porosity of 57% at x = 0.5 which indicated the higher adsorption capacity of the materials. The density of these nanoferrites varied from 2.318 to 2.590 g/cm3 with the change in their crystallite size and lattice parameter. FTIR spectroscopy also revealed two prominent peaks between 542–582 and 402–415 cm−1, representing the tetrahedral and octahedral site occupancies, occupied by Ni2+, Zn2+ and Fe3+ ions. These peaks indicated the spinel structure of the nanoferrites. The magnetic behaviour of the nanoferrites was analysed from the hysteresis loop obtained from VSM data. It was observed that the nanoferrites are highly magnetic as the value of specific saturation magnetization varied from 1.31 to 63.31 emu/g with the variation in concentration of Ni2+ metal ions ranging from x = 0.0 to x = 1.0. High values of anisotropic constant were observed, which varied from 0.00147 $$\times$$ 105 to 0.16218 $$\times$$ 105 erg/g.

Omnidirectional Reflectance of Superconductor-Dielectric Photonic Crystal in THz Frequency Range

Abstract: In this paper, we analyze the omnidirectional reflection characteristics of a superconductor photonic crystal for TE and TM modes, by using the transfer matrix method and Bloch theorem. SPC is conceived as a periodic media made of superconducting and dielectric materials. By plotting the reflectance spectra and band structures of SPC in THz frequency region, we found two ODR bands in THz frequency range for both TE and TM modes. In our work, the ODR bandgap for TM mode is wider than TE mode, which can be considered as a key feature of such SPCs. Further, we observe the effect of the variations of thicknesses of the dielectric and superconducting materials as well as the variation of the refractive index of dielectric material, on the ODR bandgaps, and some insights are drawn. It is to note that the both ODR bandgaps increase continuously with increasing the thickness of superconducting layer, while on increasing the thickness of dielectric layer, the first bandgap shows reverse effect. Moreover, the first ODR bandgap is found to be more effective at the lower refractive index of dielectric material, while the second ODR bandgap is more effective at the higher refractive index. The novel ideas from the results of ODR bandgaps for such SPCs can be used in designing reflectors or optical mirrors in THz frequency range.

Study of Electrical Transport Properties of Cadmium-Doped Zn–Mn Soft Ferrites by Co-precipitation Method

Abstract: Cadmium ion doped in Zn–Mn soft ferrites was synthesized by co-precipitation method. Cadmium content can improve the micro-structure, magnetic, electrical, optical, and vibrational properties. Single-phase cubic structure of all samples of cadmium-doped Zn–Mn soft ferrites was confirmed by using X-ray diffraction technique. Crystalline size of the material was investigated by using XRD pattern. FTIR analysis observed that the metal oxide group (M–O) exists in the presented samples. The DC resistivity decreased as the concentration of cadmium and temperature increases, and also, with the increase in cadmium contents, optical band gap decreased and Raman shift increased.

Effects of Lu3+ Doping on Microstructures and Electrical Properties of CaCu3Ti4O12 Ceramics

Abstract: The influences of Lu3+ doping on the structure and electrical properties of CaCu3Ti4O12 (CCTO) ceramics are systematically studied. We find that Lu3+ doping inhibits the grain growth of CCTO while the dielectric constant decreases firstly and then increases with the increase of Lu3+ content. The positron annihilation results indicate defect concentrations increase with the increment of Lu3+ content. At low Lu3+ doped level, the huge dielectric response of the samples mainly derives from the internal barrier layer capacitor (IBLC) effect while intrinsic polarization as defect dipoles makes more contribution at higher doped level. The dielectric loss is depressed due to the increase of cation vacancies and grain boundary resistivity. Good performances (high e′ of ∼ 1.1 × 104 and low tanδ of ∼ 0.025) at 1 kHz are obtained in Ca0.85Lu0.15Cu3Ti4O12 sample. Moreover, the enhanced nonlinear electrical properties are associated with cation vacancy defects generated by Lu3+ doping in the GB region. These findings are helpful in exploring the physical nature of the dielectric properties of CCTO.

Crystal Structure and Magnetic Properties of (Co-Ag) co-doped SnO 2 Compounds

Abstract: Pure SnO2, Sn0.94Co0.06O2, Sn0.91Co0.06Ag0.03O2, and Sn0.88Co0.06Ag0.06O2 compounds were synthesized by the solid-state reaction method. The structural characterization of these compounds by recording X-ray diffraction patterns (XRD) and analyzing them using Rietveld refinement analysis shows that these materials are in single-phase tetragonal rutile structure with typical lattice constant of a = b = 4.7385 A and c = 3.1871 A for SnO2 compound. SEM images show the formation of homogenous nanometer range spherical particles. Temperature variation of magnetization (M-T) measurements show a typical diamagnetic behavior in parent compound, while ferromagnetic (FM) to paramagnetic transition is observed in Sn0.94Co0.06O2 compound with a Curie temperature of 232.5 K. The (Co-Ag) co-doped SnO2 compounds undergo double ferromagnetic transitions. These compounds exhibit first FM transition below 620 K and another FM transition at 1108 K and 1052 K, respectively for Sn0.91Co0.06Ag0.03O2 and Sn0.88Co0.06Ag0.06O2 compounds. The measurement of magnetic hysteresis (M-H) curves at room temperature indicates the increase in coercivity and saturation magnetization values with the increase of (Co-Ag) co-doping concentration. The observed ferromagnetism was discussed based on the exchange interaction between Co2+ and Co3+ ions via oxygen vacancies.

A Theoretical Investigation on the Physical Properties of SrPd2Sb2 Superconductor

Abstract: The high temperature phase of SrPd2Sb2 polymorphs exhibits bulk superconductivity below 0.6 K. The electron phonon coupling constant and density of states are two major factors that control the superconductivity in this intermetallic compound. Here we report the detailed physical properties including structural, elastic, electronic, and optical properties of this superconducting phase by using DFT-based computational method. The calculated lattice parameters and density of states show good agreement with the experimental data. This intermetallic is ductile and comparatively soft with respect to other members of this family. This compound exhibits metallic conductivity mostly emerging from Pd and Sb atoms that is different from other similar type of superconducting materials. The strong covalent interactions in Sb-Sb and Sb-Pd bonds define the electronic characteristics of this superconducting material. The optical properties of this superconductor are fairly comparable with other similar compounds in this family.

Structural, Electronic, and Magnetic Properties of the Rare Earth-Based Solar Perovskites: GdAlO3, DyAlO3, and HoAlO3

Abstract: In this study, we use the Quantum Espresso code under the pseudo-potentials wave method based on density functional theory (DFT) to investigate the structural, electronic, and magnetic properties of the rare earth-based solar perovskites GdAlO3, DyAlO3, and HoAlO3 materials. In fact, the optimized unit cells for each one of these materials have been used to explore the stability and the ferromagnetic behavior of such materials. It is found that the cubic perovskite HoAlO3 material is the more stable structure, while the compound DyAlO3 is more stable than GdAlO3 alloy in this structure. On the other hand, the band structure and density of states confirm that the GdAlO3 perovskite has a semiconductor nature, while the DyAlO3 and HoAlO3 exhibit a half-metallic ferromagnetic character. In addition, the spin-polarized magnetic moments of these compounds reveal that these materials show a ferromagnetic nature. Moreover, the calculated magnetic moments of the cubic GdAlO3, DyAlO3, and HoAlO3 are 7.02 μB, 5.00 μB, and 4.00 μB, respectively. Furthermore, the obtained results approve that these compounds could be promising materials for spintronic and optoelectronic devices. Moreover, such materials are promising candidates for photovoltaic applications.

Spintronics and Innovative Memory Devices: a Review on Advances in Magnetoelectric BiFeO3

Abstract: Advances in magnetoelectric BiFeO3 open the opportunity to commercialize innovative memory devices. Spin-based technology was employed to fabricate the magnetic random access memory (MRAM). The ferroelectric random access memory (FeRAM) based on ferroelectricity was also realized. Both memories have great properties, but unfortunately with some flaws. A new vision was hypothesized to combine both memories to create unlimited memory device. Combination of MRAM and FeRAM means coupling of ferromagnetic-ferroelectric properties in single material. Studies on magnetoelectric BiFeO3 might hold the future for memory devices with thousands of published papers in last years. In this review, we tried to show a comprehensive picture of the large number of studies on multiferroic BiFeO3 including techniques to enhance the properties and remove obstacles. Here, we begin with an overview of spintronics memory devices and multiferroic materials. An organized classification of studies depended on occupation site in BiFeO3 and type of dopant was presented.

Manifestation of Magnetic Characteristics of Zinc Ferrite Nanoparticles Using the Langevin Function

Abstract: Zinc ferrite (ZnFe2O4) nanoparticles were prepared by chemical co-precipitation method. Structural characterization was performed using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Formation of spinel phase was confirmed from XRD studies. Crystallite size and lattice constant of the prepared sample were calculated. TEM images reveal spherical-shaped particles with nanosized distribution. Room temperature magnetic hysteresis loop was recorded using vibrating sample magnetometer (VSM). The magnetization loops exhibit a very narrow loop and behave like superparamagnetic nature. Using the Langevin function, the magnetic behaviour of the prepared nanoparticles was investigated. From the curve fitting, saturation magnetization and reduced magnetization were determined. As-prepared sample was further annealed at three different temperatures namely 800 °C, 1000 °C, and 1200 °C for 2-h duration. The effects of annealing on the structural and magnetic properties were further investigated using XRD and VSM. The observed results on the magnetic characteristics of ZnFe2O4 and applicability of the Langevin function are being discussed.

Investigation of Structural, Electronics, Optical, Mechanical and Thermodynamic Properties of YRu2P2 Compound for Superconducting Application

Abstract: The structural, electronic, optical, and thermodynamic properties of the YRu2P2 superconductor are investigated theoretically using the CASTEP (Cambridge Serial Total Energy Package) code, which utilizes an ultra-soft pseudopotential USP plane wave and a Perdew Burke Ernzerhof (PBE) exchange–correlation functional of the Generalized Gradient Approximation (GGA). The evaluated value of the lattice parameters is found to be 4.84 A. The band structure of the compound indicates that this compound does not possess the band gap. The absence of the band gap suggests that the compound has a metallic nature. The density of states (partial and total) verifies the findings obtained from band structure. The existence of strong ionic contact between Ru–Ru atoms is shown by the negative value of the Mulliken population. The research has also been done on the optical properties of the material to find out how it responds optically. The results of the elastic constant calculation show that the material is mechanically stable and brittle in its natural state. The positive value of AU indicates that the compound is anisotropic. It is also revealed from the AG and AB values that the compound has anisotropic characteristics. Vickers hardness value obtained for the compound demonstrates that it is relatively hard in nature. Along with the initial elastic modulus calculation, the bulk, shear, and Young’s modulus are also determined. The existence of covalent character in the compound is shown by the Poisson’s ratio. The thermal conductivity, melting point, and Dulong-Petit limit of the material have all been determined to perform a more in-depth analysis of the material. The overlapping of the Fermi bands shows that the material is a superconductor, and the material’s metallic nature suggests that it will be an excellent reflector of incoming light.

Doping Effect of Cobalt on Various Properties of Nickel Oxide Prepared by Solution Combustion Method

Abstract: Pure and cobalt-doped (Co-2 to 10 mol%) nickel oxide (NiO) powder samples were prepared by solution combustion method and annealed at 600 °C for 2 h. The crystalline and structural properties were characterised by using X-ray diffraction (XRD) and Raman spectroscopy. Field emission scanning electron microscope (FESEM) and energy-dispersive spectroscopy (EDAX) techniques were used to study the surface morphology and characteristic elements present in samples. Higher value of retentivity (12.20 × 10−2 emu/g) and coercivity (900 Oe) is found for 10 mol% Co-doped NiO, which is much higher than pure NiO. Such properties improve the magnetic memory and hardness of a magnetic material. A decrease in an optical band gap from 2.67 to 2.05 eV was observed for pure and Co-doped (2 to 10 mol%) NiO powder samples, which is quite useful in optoelectronic devices. Maximum value of conductivity (11.23 × 10−6 Ω−1 cm−1) and dielectric constant (204) is found for Co 6 mol%-doped NiO. All the measurements were recorded at room temperature so as to utilise them for device fabrication readily. A significant improvement in magnetic, optical and dielectric properties was observed for NiO with increasing concentration of cobalt, which makes it a better choice for spintronic, optoelectronic, magnetic and storage devices.

Electronic and Magnetic Properties of Chemical Solution Deposited BiFeO3 Thin Film: a Soft X-ray Magnetic Circular Dichroism Study

Abstract: In this work, we report the electronic and magnetic properties of epitaxial BiFeO3 (BFO) thin film deposited on SrTiO3 (001) substrate via the chemical solution deposition technique. These properties of pure BFO thin films were characterized by X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism techniques (XMCD). The large magnetization at Fe-edge could be due to annealing in nitrogen. Annealing in nitrogen atmosphere increases the grain size and porosity which lead to create more oxygen vacancy. The presence of oxygen vacancies which compensate the bismuth vacancies created due to bismuth volatilization. The origin of large orbital momentum in BFO thin film is also discussed. The O K-edge spectra display large spectral variation depending on the polarization vector E. The structural distortion at oxygen octahedral induces large anisotropy due to Fe 3d–O 2p hybridization. The hybridized Fe 3d orbitals contribute a much larger orbital momentum in BFO thin film.

Aspects of Topological Superconductivity in 2D Systems: Noncollinear Magnetism, Skyrmions, and Higher-order Topology

Abstract: The review is aimed at highlighting the aspects of topological superconductivity in the absence of spin–orbit interaction in two-dimensional systems with long-range noncollinear spin ordering or magnetic skyrmions. Another purpose is to give a brief introduction to the new concept of topological superconductivity, i.e. higher-order topology in two-dimensional systems including spin–orbit coupled structures. The formation of Majorana modes due to magnetic textures is discussed. The role of effective triplet pairings and odd fermion parity of the ground state wave function in different systems is emphasized. We describe the peculiarities of the magnetic skyrmions, leading to the formation of the Majorana modes and defects on which the modes are localized. The problem of braiding in the two-dimensional systems, especially in higher-order topological superconductors, is considered.

Role of Nature of Rare Earth Ion Dopants on Structural, Spectral, and Magnetic Properties in Spinel Ferrites

Abstract: In this research work, the effect of ionic radii of various rare earth ions on structural and magnetic properties of spinel ferrites having the composition MFe2-yREyO4 (y = 0, 0.2) (where M = Cu, Cd, Ni, Zn, Mn, and RE = La, Ce, and Tb and Dy) have been studied. XRD reflections for Tb3+/Dy3+ and Ce3+ substitution ensured phase purity of FCC structure formation with no additional impurities. But we have observed secondary phases for lanthanum substituted spinel ferrites due to its larger ionic radii as compared to host crystal. Crystallite sizes and lattice parameters are found to show decreasing trend with decreasing ionic radii of dopant rare earth ions. The magnetic parameters for all prepared samples were discussed by tracing hysteresis curves measured at room temperature. VSM data demonstrated that magnetization of investigated samples was found to be increased with substitution of larger ionic radii ions which is attributed to spin-canting effect and increase of crystallite. Furthermore, the dopants having smaller ionic radii have possessed high coercivity and improved initial permeability. On the basis of these characteristics, these synthesized materials could be suggested for various industrial and technological applications.

Temperature-Dependent Variations in Structural, Magnetic, and Optical Behavior of Doped Ferrites Nanoparticles

Abstract: Nanocrystalline Mn-Zn ferrite nanopowders (Mn0.5Zn0.5Fe2O4) were synthesized by co-precipitation technique and post-fabrication annealing has been performed at different temperature ranges from 400 to 700 °C for 2 h. The effect of annealing on morphology, crystalline phase formation, cation distribution, lattice constant, particle size, magnetic properties, and optical properties was studied by scanning electron microscopy (SEM), x-ray diffraction (XRD), vibrating sample magnetometer (VSM), and UV-visible spectroscopy (UV-Vis) respectively. The crystallite size increased from 14 to 24 nm with the annealing temperature owing to the grain growth process or more technically we say Ostwald ripening mechanism. The decomposition of ferrites at low-temperature results in the formation of hematite Fe2O3 eventually reduced the magnetic properties of ferrites. The hematite, impurity phase, started to dissolve or converted into the ferrite phase after 600 °C. The sample annealed at 700 °C shows a better crystalline structure, phase formation, and larger magnetization compared to the other ferrite samples. The improved magnetic behavior after heat treatment is due to the better alignment of domains at the cost of the grain growth process. The UV-Vis spectroscopy result revealed the maximum absorbance at 380 nm.

Dynamic Identification of HTS Maglev Module for Suspended Vehicle by Using a Single-Degree-of-Freedom Generalized Bouc–Wen Hysteresis Model

Abstract: The energy dissipation phenomenon of a high-temperature superconducting (HTS) magnetic levitation (Maglev) transport system is investigated by using a single degree of freedom generalized Bouc–Wen hysteresis model. The Maglev system under test consists of a bogie with HTS skaters, which interacts with permanent magnets distributed on the guideways; thanks to a passive and self-balanced magnetic interaction, the vehicle is suspended and guided in all phases of the motion, including zero speed. The response of the HTS skate is tested under pseudo-static cyclic load in the vertical and lateral directions. The parameters of the generalized Bouc–Wen (GBW) model are calibrated on the experimental hysteresis loops using an ordinary least squares–based algorithm. The vertical dynamics of the levitating HTS skate is affected by the magnetic field discontinuities of the guideway. The dissipated hysteretic energy is simulated to assess the dependence on the velocity and pattern of the magnetic field. The displacement response is obtained by solving the nonlinear differential equation representative of the moving HTS skater, modelled as a single degree of freedom system, whose interactions with the magnetic guideway are described by the identified GBW hysteresis law.

Transport Properties of Ce-Doped Cd Ferrites CdFe2−xCexO4

Abstract: Cadmium ferrites belong to normal spinel ferrites, and they exhibit interesting electrical, magnetic, and optical properties. The pure and cerium-doped cadmium ferrites CdFe2−xCexO4 (x = 0.0, 0.125, 0.250, 0.375, 0.5) were synthesized by a chemical co-precipitating technique using sodium hydroxide as a co-precipitating agent. The structures and phase purity of fabricated nanomaterials were analyzed by X-ray diffraction (XRD). The crystallite size for all the prepared nanomaterials was in the range of 28–46 nm. The lattice constant and unit cell volume were found to decrease with the increasing concentration of Cerium, which was confirmed by the peak shift in the XRD pattern. The X-ray density for all nano ferrites increased with the enhancement of cerium composition. The resistivity of the nanomaterials has random behavior with the enhancement of cerium composition for a temperature, but the value of resistivity at x = 0.125 has the lowest value and at x = 0.375 has the highest value for almost all temperatures. For specific concentrations, a decreasing trend of resistivity of fabricated materials was found with an increment of temperature. The activation energies were also calculated, and it increased for x = 0.125 and then decreased for all the nanomaterials. For the confirmation of the M–O bonds, FTIR analysis of all the nano ferrites was also performed. The analysis shows a higher frequency absorption band in the range of 531.24–534.84 cm−1. This absorption band confirms that metal oxides are formed in all the synthesized nanoparticles.

Influence of Ba2+ Doping on Structural and Electrical Transport Properties of YMnO3 Ceramics

Abstract: The pristine and barium (Ba2+) doped YMnO3 (Y1−xBaxMnO3; x = 0.00 and 0.05) ceramic samples were synthesized through the solid-state reaction method. The X-ray diffraction, Raman spectroscopy, and scanning electron microscopy were performed for the structural and morphological studies. The electrical transport properties were investigated using dielectric and modulus spectroscopy. The XRD patterns of the titled ceramics have shown the monophasic hexagonal structure having P63cm space group symmetry. The average crystallite size is found to decrease on partial substitution of Ba2+ cation. Raman spectroscopy was performed to observe the local disorder and variation in the modes with the introduction of dopant in the pristine ceramic. The surface morphology displays the formation of non-uniform grains in the ceramics. The dielectric spectroscopy reveals a decreasing trend in both the dielectric constant and dissipation factor with increasing frequency. It indicates the significant role played by the space charge polarization. The electrical modulus study of the ceramics was also performed to explore the electrical transport phenomenon. The present study reports the enhanced dielectric nature of doped materials.

Investigations on the Structural and Electrical Properties of Sm3+-Doped Nickel Ferrite–Based Ceramics

Abstract: Compositions of ferrimagnetic NiSmxFe2−xO4 (0.00 ≤ x ≤ 0.25) ceramics were synthesized by the self-propagating sol-gel autocombustion method. Structural information was found using X-ray diffraction. It reveals that all the ceramics possess cubic symmetry of spinel ferrite with a small amount of orthoferrite phase SmFeO3, which is a ferroelectric material. The amount of phases and lattice parameter were determined by the Rietveld refinement method using the Fullprof suite software. As doping concentration increases, the secondary phase fraction of the ferroelectric SmFeO3 also increases. Due to the increase of the ferroelectric phase in NiFe2O4, the electrical properties of doped samples also modify. To know this modification, the electrical properties of these samples have been investigated. The room temperature dielectric and complex impedance analysis have been measured in the frequency range of 1–106 Hz. The dielectric behavior for x = 0.05 concentration (NiSm0.05Fe1.95O4) has a maximum dielectric constant value with a minimal loss tangent. Cole-Cole plot brings out the role of grain and grain boundaries in the bulk. Using impedance study, the resistance and capacitance of grain and grain boundaries have been determined. The ferroelectric behavior has been performed through the P-E (polarization versus electric field) and J-E (leakage current versus electric field) curves at room temperature.

Does Brian Josephson’s Gauge-Invariant Phase Difference Live on a Line or a Circle?

Abstract: This article, written to honor Brian Josephson on the occasion of his 80th birthday, discusses the topological nature of an emergent collective variable, namely the gauge-invariant phase difference across the two leads of a superconducting tunnel junction, which plays a central role in Josephson’s discovery of the effect bearing his name.