Magnetic Properties Of Materials Research Articles

Preparation of the graphene-based smart hydrophobic nanocomposite and its application in oil/water separation.

Designing and synthesizing materials with smart hydrophobicity against an external magnetic field for efficient oil/water separation is of great importance due to the increasing problems caused by oil pollution. Here,the nanocomposites were fabricatedbased on graphene and different iron oxides exhibit smart hydrophobicity against an external magnetic fieldand they arein powder form eliminating the requirementfor a substrate employing a facile and echofriendly method. The results prove that autoclaving of graphene leads to its ferromagnetic property; then it is attached to iron oxides by magnetic attraction and a nanocomposite is produced. The magnetic property of the resulting nanocomposite is higher than the magnetic property of its individual components. In addition, following nanocomposite formation, its hydrophobicity and surface area also change. FESEM images were taken from the nanocomposites to study their surface morphology, and EDS-MAP analysis to observe the elemental distribution uniformity of the nanocomposites. Also, to measure the surface area and pore size, BET analysis has been performed on pure materials and graphene-black iron oxide nanocomposite (graphene@black iron oxide). The results show that the specific surface area of black iron oxide increases after being composited with graphene dispersed at 5000rpm. Indeed, graphene forms a composite by binding to iron oxide, and therefore, its specific surface area increases compared to iron oxide and graphene alone. These results show an increase in oil sorption and better separation of oil from water by the prepared nanocomposite. Also, to measure the magnetic properties of pure materials, graphene@black iron oxide, and ferromagnetic graphene at 3000 and 5000rpm, the Vibrating Sample Magnetometeranalysis has been performed. The results have proven that the nanocomposite powder prepared by a simple method obtained from cost-effective and available materials is hydrophobic and becomes more hydrophobic by applying an external magnetic field. Due to the ease with which oil can be readily removed from the nanocomposite by eliminating the external magnetic field, this nanocomposite is an excellent choice for the separation of oil from water.

A semi-analytical approach for two-dimensional frictional contact of anisotropic magneto-electro-elastic solids

In this work, we present a semi-analytical modeling approach for solving the frictional contact of two-dimensional anisotropic magneto-electro-elastic (MEE) solids. The method is established in a broad framework in which the contact body is made of generally anisotropic MEE materials, the punch head can be arbitrary, and the punch can be subjected to generalized loading conditions including mechanical forces and electric and magnetic charges. An analytical solution of generalized distributed load along the half-plane surface is derived and utilized to formulate the semi-analytical equations governing the relation between the generalized displacements and tractions. Based upon the semi-analytical equations, the semi-analytical model in which the influence matrices can be calculated explicitly and its effectiveness is established. An iterative procedure is then used for determining the contact region, contact status, generalized surface deformation and the distribution of contact tractions, as well as the punch’s indentation depth and electric and magnetic potentials. The present approach is verified by comparing its numerical results with those obtained by the existing analytical solutions and boundary element method. The influences of different factors, such as punch profile, mechanical load, electric and magnetic charges, friction coefficient and material properties, are also analyzed. The capability of this method to handle complicated geometry, such as rough surfaces, is finally discussed, showing the potential performance of the developed method for practical engineering applications.

EFFECT OF SILICON RUBBER (SIR) IN FABRICATION OF NdFeB/BaFe12O19-BASED HYBRID MAGNET

The purpose of this study was to determine the effect of physical properties (density), magnetic properties (magnetic flux), and mechanical properties (tensile strength) of NdFeB- BaFe12O19 hybrid magnets with silicon rubber adhesive. NdFeB - BaFe12O19 permanent magnet has been made with a silicon rubber (SIR) adhesive mixture. The percentage variations of magnetic powder materials used are NdFeB: BaFe12O19 (95%: 5%) and NdFeB: BaFe12O19 (90%: 10%) mixed with a weight percentage of silicone rubber with variations of 20%, 40%, 60% and 80%. Characterization includes physical properties in the form of density where the sample with 20% SIR variation has the largest bulk density value of 3.28 g/cm3 for NdFeB: BaFe12O19 (95%: 5%) and 3.24 g/cm3 for NdFeB: BaFe12O19 (90%: 10%), and mechanical properties in the form of tensile strength where the most optimum elasticity value is at 80% silicone rubber. Meanwhile, the most optimum magnetic properties of materials are owned by material samples with variations of SIR at a concentration of 20% for sample variations of 95% NdFeB and 5% BaFe12O19, which is 602.8 Gauss.

Enhanced TCR and MR by grain boundary modification and phase competition in La0.67Ca0.33MnO3: Aux (x=0, 0.05, 0.1, 0.15) composite ceramics

La0.67Ca0.33MnO3 (LCMO) ceramics exhibit high temperature coefficient of resistance (TCR) and colossal magnetoresistance effect (CMR). Increasing their TCR and MR values can enhance potential applications in uncooled infrared detectors and magnetic storage devices. However, presence of inherent grain boundaries and defects within these ceramics significantly limits their performance. Therefore, this work proposed modifying grain boundaries of LCMO ceramic using low-resistivity and stable Au to enhance its electrical transport and improve magnetoresistance performance through competition between antiferromagnetic Au and ferromagnetic La0.67Ca0.33MnO3. A series of La0.67Ca0.33MnO3: Aux (x = 0, 0.05, 0.10, 0.15) composite ceramics was prepared by sol-gel and solid-state methods. Introduction of Au increased TCR from 40.1 %·K−1 to 55.2 %·K−1 and MR from 60.4 % to 74.2 %, when x = 0.10. This study demonstrates that proposed strategy involving multiphase interactions can significantly improve electrical transport and magnetic properties of functional materials, with promising applications in areas such as thermoelectric and magnetoelectric conversion.

Investigation of variety of valence metal ions combinated novel Co‐rich high entropy oxides and its magnetic properties and microstructure

In this work, a series of five spinel-structured oxides were synthesized using a straightforward and effective solid-state methodology. Departing from the conventional design concept, we opted for the substitution of Fe3 + with five metal cations, all possessing trivalent average valence states and equivalent proportions. X-ray diffraction, scanning electron microscope, energy spectrum analyzer, vibrating sample magnetometer were used to detect the phase, micro-structure, element distribution, magnetism of the samples, respectively. The test results show that samples have the spinel structure (Fd3(_)m), and the element composition and distribution are the same as expected. The test results of magnetic properties reveal that these five samples exhibit the properties of soft magnetic materials. The maximum adjustment range of saturation magnetization (Ms) is increased from 23.5 emu/g to 34.8 emu/g by adjusting the elemental composition. Besides, the maximum adjustment range of coercivity (Hc) is increased from 11 Oe to 60 Oe. Furthermore, these materials exhibit a low remanent magnetization ratio, indicating that high-entropy oxides with spinel structures are highly sensitive to changes in an applied magnetic field. The high-entropy oxide is a new material with great prospect. It creates new possibilities for the design of magnetic materials.

Advances in organic–inorganic nanocomposites for cancer imaging and therapy

Abstract “All in one” organic–inorganic nanocomposites with high biocompatibility and excellent physicochemical properties have recently attracted special attention in cancer imaging and therapy. Combination of organic and inorganic materials confers the nanocomposites with superior biocompatibility and biodegradability of organic materials, as well as magnetic, mechanical, and optical properties of inorganic materials. Increased endeavors have been made to produce diverse organic–inorganic nanocomposites and investigate their potential applications in cancer treatment. Thus, a systematic review of research progresses of diverse organic–inorganic nanocomposites in cancer imaging and therapy is indispensable. Following a brief overview of nanocomposites synthesis, classification, and functionalization, the current review is focused on comprehensively summarizing representatives of both organic–inorganic nanoscale nanocomposites (including organic-silica, organic-carbon, organic-quantum dots, organic-platinum family metals, organic-gold, organic metal oxides, and other nanocomposites) and organic–inorganic molecular nanocomposites (including metal-organic frameworks, organosilica nanoparticles, and amorphous metal coordination polymer particles), and further analyzing their working mechanism in cancer imaging and therapy. Finally, the challenges and future perspectives of organic–inorganic nanocomposites are addressed for promoting their developments and clinical application in cancer treatment.

High Gas Pressure and High-Temperature Synthesis (HP-HTS) Technique and Its Impact on Iron-Based Superconductors

The high-pressure growth technique generally plays an important role in the improvement of sample quality and the enhancement of various physical and magnetic properties of materials. The high gas pressure technique provides a large sample space (10–15 cm) to grow various kinds of materials. In this paper, we introduce the high gas pressure and high-temperature synthesis (HP-HTS) technique that is present at our institute and is applied to the growth process of different kinds of superconducting materials, particularly iron-based superconductors. More details and the working principle of this HP-HTS technique are discussed. We have also demonstrated the current results based on iron-based superconductors by using this unique HP-HTS technique. These results demonstrate the enhancement of the superconducting properties with improved sample quality compared to the conventional synthesis process at ambient pressure.

Iron–palladium nanoparticle biocomposites with increased metal loading

Biocomposites containing magnetic nanoparticles have the potential to combine the unique, tunable properties of nanoparticles with the strong mechanical and environmentally sustainable properties of natural fibers like cotton. Recently, a method to synthesize Fe–Pd nanoparticles on cellulose has been developed. This study presents a detailed investigation on how the structural and magnetic properties of these nanoparticle biocomposite materials are affected by increasing metal loading with respect to the cellulose while maintaining a fixed 1:1 Fe:Pd atomic ratio. Infrared spectroscopy and electron microscopy (SEM and TEM) indicate that spherical Fe–Pd nanoparticles (approximately 3–8 nm in diameter) are distributed heterogeneously throughout the fiber matrix along with amorphous iron oxide, while XRD suggests the dominant crystalline phase within the nanoparticles is likely FePd3 under significant strain. The magnetic response of the biocomposites in static and dynamic magnetic fields (as a function of frequency and temperature) reveals a polydisperse ensemble of Fe–Pd nanoparticles with up to four distributions of blocking temperatures. The lower temperature distributions are prevalent at low metal loading. As the metal loading increases, the higher temperature distributions emerge, while the lower temperature distributions are suppressed. This result points towards enhanced nanoparticle heterogeneity and agglomeration as the metal loading increases.

Atomic-scale structure of RCo2 (R[dbnd]Tb,Dy) compounds studied by X-ray diffraction and pair distribution function analysis

The RCo2 compounds have attracted lots of research interests due to the giant magnetostriction effect. The average structure of these compounds have been well established, but the studies on the local structure are still rare. In this paper, the average structure and the local structure of the RCo2 (RTb, Dy) compounds were investigated with a combination of X-ray diffraction (XRD) and pair distribution function (PDF) analysis, and the electronic structure were studied by the first principle calculations. The results demonstrate that these two compounds present MgCu2-type cubic structure at both average and local scale at room temperature. The variation of the R–Co bond length is much larger than that of the Co–Co bond length with changing R element. The Co–Co bond of TbCo2 compound shows abnormal change around the structural transition. The hybridization between R-5d state and Co-3d state strongly affect the R–Co bond, while the magnetic polarization of Co-3d state show stronger effect on the Co–Co bond. These findings highlight the important role of atomic-scale structure in determining the magnetic properties of the RCo2 materials.

The on-chip scanning probe with dual niobium nitride nanoscale superconducting quantum interference devices for magnetic imaging at the high temperature

The scanning superconducting quantum interference device (SQUID) microscope is a powerful tool for investigating the microscale magnetic properties of quantum materials. However, the low operating temperature of SQUIDs limits the application of the microscope. In this work, we developed an on-chip probe with dual niobium nitride (NbN) nano-SQUIDs for scanning SQUID microscope. The working temperature of the NbN nano-SQUID on-chip probe was up to 8 K, and it enabled the magnetic imaging of samples at the temperature up to 128 K. We used a gradiometric readout scheme for dual nano-SQUIDs in one probe to reduce the influence of the background magnetic field. Furthermore, we demonstrated the capabilities of both topographic and current imaging by the on-chip probe with spatial resolutions of 1 μm and 2 μm, respectively. The advantage of the probe at the high temperature was also demonstrated by the investigation of the superconducting vortices distribution in the yttrium-barium-copper-oxide film.

Optimizing experimental parameters for orbital mapping

A new material characterization technique is emerging for the transmission electron microscope (TEM). Using electron energy-loss spectroscopy, real space mappings of the underlying electronic transitions in the sample, so called orbital maps, can be produced. Thus, unprecedented insight into the electronic orbitals responsible for most of the electrical, magnetic and optical properties of bulk materials can be gained. However, the incredibly demanding requirements on spatial as well as spectral resolution paired with the low signal-to-noise ratio severely limits the day-to-day use of this new technique. With the use of simulations, we strive to alleviate these challenges as much as possible by identifying optimal experimental parameters. In this manner, we investigate representative examples of a transition metal oxide, a material consisting entirely of light elements, and an interface between two different materials to find and compare acceptable ranges for sample thickness, acceleration voltage and electron dose for a scanning probe as well as for parallel illumination.

Advantages of Ferroelectrics as a Component of Heterostructures for Electronic Purposes: A DFT Insight.

The main advantage of using ferroelectric materials as a component of complex heterostructures is the ability to tune various properties of the whole system by means of an external electric field. In particular, the electric field may change the polarization direction within the ferroelectric material and consequently affect the structural properties, which in turn affects the electronic and magnetic properties of the neighboring material. In addition, ferroelectrics allow the electrostriction phenomenon to proceed, which is promising and can be used to affect the magnetic states of the interface state in the heterostructure through a magnetic component. The interfacial phenomena are of great interest, as they provide extended functionality useful for next-generation electronic devices. Following the idea of utilizing ferroelectrics in heterostructural components in the present works, we consider 2DEG, the Rashba effect, the effect of magnetoelectric coupling, and magnetostriction in order to emphasize the advantages of such heterostructures as components of devices. For this purpose, model systems of LaMnO3/BaTiO3, La2CuO4/BaTiO3, Bi/BaTiO3, and Bi/PbTiO3, Fe/BaTiO3 heterostructures are investigated using density functional theory calculations.

Electron spin resonance in emerging spin-driven applications: Fundamentals and future perspectives

Spin, the intrinsic angular momentum of an electron, is increasingly being recognized as a versatile tool in the development of next-generation technologies, including quantum computing, sensing, and communication, which exploit quantum phenomena. The burgeoning theoretical understanding coupled with technological advancements have catalyzed research efforts aimed at controlling and manipulating the optical, electrical, magnetic, and thermal properties of materials through the modulation of spin states. Among the myriad of techniques available for investigating these spin-dependent properties, Electron Spin Resonance (ESR), sometimes referred to as electron paramagnetic resonance, stands out as one of the most direct and potent methods to probe electron spin dynamics irrespective of the material environment. ESR furnishes insightful data on the states of individual spins and clusters, spin coherence via relaxation time measurements, and inter-spin distances from spin–spin interaction measurements. Additionally, ESR facilitates the manipulation of spin systems by tailoring the Zeeman energy through the modulation of the external magnetic field, and critically, by the remote manipulation of spins via the application of microwave pulses at resonance frequencies. Modern ESR experimental setups are versatile and can be employed across a wide temperature spectrum—from a few Kelvin, where quantum effects are pronounced, to room temperature and beyond. This adaptability enhances the utility of ESR in investigating the spin-dependent properties in condensed matter systems. Notwithstanding the tremendous potential and advantages that ESR offers, it remains underutilized, especially when compared to inelastic neutron scattering (INS) and nuclear magnetic resonance, despite the latter being more expensive and INS being less accessible. In this review, we elucidate the fundamental principles of ESR, with an emphasis on magnetic and spin interactions in solids, and explore the potential of ESR in advancing the understanding of spin properties across a diverse array of materials science disciplines. We commence with a concise introduction to spin-related physics, followed by the application of ESR in characterizing spin systems. As such, this review aims to serve as a valuable resource for a broad audience, ranging from novices to experts, who are keen on unraveling spin phenomena and dynamics in materials science and condensed matter physics.

Investigative study on the properties of magnetic materials for electrical machines

<p><span>The paper attempts to investigate the properties of the magnetic materials used in the construction of rotating electric machines, with a view to arrive at the appropriate choice for the induction motors in particular. Measurement of magnetic properties for rotating electrical machines are more important to both machine designer and operator. This paper discusses the influence of magnetic properties of electrical steel on performance of electrical machine. Here properties like BH curve, core loss, permeability and other vital parameters are measured using 400×400 Epstein tester over wide range flux density and frequency up to 50 Hz and 400 Hz. The results measured in terms of the core loss, BH curve and permeability showcase the benefits to decide on the suitability of the material for use in practice.</span></p>

Magnetic and Electrical Properties of CoRE2W2O10 Ceramic Materials.

Microcrystalline samples of CoRE2W2O10 tungstates (RE = Y, Dy, Ho, Er) were prepared by a high-temperature solid-state reaction and then sintered into a ceramic form for unique properties and potential applications. For this purpose, structural, microscopic, ultraviolet-visible (UV-vis), magnetic, electrical, and thermoelectric measurements were performed. These studies showed a monoclinic structure, paramagnetism, short-range antiferromagnetic interactions in all samples, long-range ferrimagnetic interactions only in CoY2W2O10, poor n-type conductivity of 6.7 × 10-7 S/m at room temperature, strong thermal activation (Ea1 = 0.7 eV) in the intrinsic region, a strong increase in the power factor (S2σ) above 300 K, a Fermi energy (EF) of 0.16 eV, and a Fermi temperature (TF) of 1800 K. The above studies suggest that anion vacancy levels, which act as doubly charged donors, and to a lesser extent, the mixed valence band of cobalt ions (Co2+, Co3+), which are located below the bottom of the conduction band and below the Fermi level, are responsible for electron transport.

Magnetic States and Electronic Properties of Manganese-Based Intermetallic Compounds Mn2YAl and Mn3Z (Y = V, Cr, Fe, Co, Ni; Z = Al, Ge, Sn, Si, Pt).

We present a brief review of experimental and theoretical papers on studies of electron transport and magnetic properties in manganese-based compounds Mn2YZ and Mn3Z (Y = V, Cr, Fe, Co, Ni, etc.; Z = Al, Ge, Sn, Si, Pt, etc.). It has been shown that in the electronic subsystem of Mn2YZ compounds, the states of a half-metallic ferromagnet and a spin gapless semiconductor can arise with the realization of various magnetic states, such as a ferromagnet, a compensated ferrimagnet, and a frustrated antiferromagnet. Binary compounds of Mn3Z have the properties of a half-metallic ferromagnet and a topological semimetal with a large anomalous Hall effect, spin Hall effect, spin Nernst effect, and thermal Hall effect. Their magnetic states are also very diverse: from a ferrimagnet and an antiferromagnet to a compensated ferrimagnet and a frustrated antiferromagnet, as well as an antiferromagnet with a kagome-type lattice. It has been demonstrated that the electronic and magnetic properties of such materials are very sensitive to external influences (temperature, magnetic field, external pressure), as well as the processing method (cast, rapidly quenched, nanostructured, etc.). Knowledge of the regularities in the behavior of the electronic and magnetic characteristics of Mn2YAl and Mn3Z compounds can be used for applications in micro- and nanoelectronics and spintronics.

Detailed investigation on structural, optical, dielectric and magneto-dielectric properties with enhanced magneto-impedance characteristic of NdFeO3 nanoparticles

NdFeO3 (NFO) was synthesized using sol-gel citrate method and subsequent calcination at 1023 K. Utilizing Rietveld refinement analysis of the XRD pattern, it has been verified that NFO exhibits an orthorhombic crystal structure, with space group Pbnm. NFO grains were seen to be strongly agglomerated in a SEM image, despite their irregular shapes. The analysis of optical properties revealed a transmittance range of ∼20%–∼50% and an optical band gap of 2.15 eV for the NFO material. The dielectric properties of NFO were analyzed with respect to their dependence on frequency and temperature, while the ac electrical conductivity was studied in terms of its frequency variation. The dielectric dispersion behavior of NFO is explained by Maxwell Wagner-type polarization. A negative magneto-dielectric (MD) coupling of −19% and −35% was measured for ε and tanδ at 1 kHz for NFO. Magneto-impedance measurements on NFO showed positive magneto-resistance and both positive and negative magneto-capacitance, suggesting that the grain effect had a substantial role in the material's magnetic properties. These results suggest that NFO is an excellent choice for memory-based electronic devices with an appropriate band gap for optoelectronic applications having a large MD effect.

Measurement and analysis of magnetic properties under SVPWM excitation for soft magnetic composites (SMCs) and silicon steel

This study developed a system for measuring the magnetic properties of soft magnetic materials under space vector pulse width modulation (SVPWM) excitation, enabling testing at different modulation indexes, frequencies, and carrier frequencies. Two types of soft magnetic materials were tested, and the effects of SVPWM waveform parameters on material loss were analyzed. The results show that the loss of SMCs is higher than that of silicon steel when the max magnetic flux density is close to 1.5 T. In contrast, at the modulation frequencies are 100 Hz and 200 Hz, the loss of SMCs is lower than that of silicon steel. The reliability of the testing system was validated through magnetic characterization of the two materials, providing a reference for their application and preparation.

Magnetic Property, Heat Capacity and Crystal Structure of Mononuclear Compounds Based on Substitute Tetrazole Ligand.

Three mononuclear compounds formulated as {M[(2-1H-tetrazol-5-yl)pyridine]2(H2O)2} (M = FeII (1), CoII (2), CuII (3)) were reported and synthesized. Their space group is monoclinic, P21/c, revealed by single-crystal X-ray diffraction. Antiferromagnetic interactions exist in Compounds 1, 2 and 3, as evidenced by magnetic and low-temperature heat capacity measurements. In addition, their thermodynamic functions were determined by a relaxation calorimeter, indicating that Compound 1 exhibits a Schottky anomaly in low-temperature heat capacity. This work can provide an important fundamental basis for the research of the thermophysical properties of molecular-based magnetic materials.

In unison magnetization reversal in a magnetoelastic bilayer structure

Due to the magnetostriction effect, a magnetic material changes its dimensions when it is magnetized. In this work, we show how in a magnetostrictive bilayer structure comprising two materials with magnetostriction constants of opposite signs, the magnetic switching is affected by magnetoelastic coupling. While the layer with positive magnetostriction tries to elongate in the direction of the applied magnetic field, the layer with negative magnetostriction tries to contract. In the studied bilayers, the mechanical influence of each magnetostrictive layer on the other is of the opposite sign because of their opposite magnetostrictive constants. Since magnetoelasticity is not an interfacial interaction but an intrinsic property of magnetic materials, the mechanical strain promoted by the applied magnetic field affects the layers as a whole. The net effect is a simultaneous reversal of magnetization of the two layers regardless of their thicknesses. This behavior has been studied in bilayers with different thickness ratios comprising Ni90Fe10, negative magnetostriction and Fe70Ga30, positive magnetostriction. These results demonstrate the possibility of using this physical mechanism to beat the critical limit thickness imposed by interfacial interactions in magnetically coupled multilayers in such a way that the magnetization reversal is made in unison regardless of the layer thickness.