State-of-the-art developments in metal and carbon-based semiconducting nanomaterials： applications and functions in spintronics, nanophotonics, and nanomagnetics

Nanomaterials composed of metals and metal alloys are the most valuable components in emerging micro- and nano-electronic devices and innovations to date. The composition of these nanomaterials, their quantum chemical and physical properties, and their production methods are in critical need of summarization, so that a complete state of the art of the present and future of nanotechnologies can be presented. In this review, we report on the most recent activities and results in the fields of spintronics, nanophotonics, and nanomagnetics, with particular emphasis on metallic nanoparticles in alloys and pure metals, as well as in organic combinations and in relation to carbon-based nanostructures. This review shows that the combinatory synthesis of alloys with rare metals, such as scandium, yttrium, and rare earths imparts valuable qualities to high-magnetic-field compounds, and provides unique properties with emphasis on nanoelectronic and computational components. In this review, we also shed light on the methods of synthesis and the background of spintronic, nanomagnetic, and nanophotonic materials, with applications in optics, diagnostics, nanoelectronics, and computational nanotechnology. The review is important for the industrial development of novel materials, and for summarizing both fabrication and manufacturing methods, as well as principles and functions of metallic nanoparticles.

Coercivity mechanisms in nanostructured permanent magnets

Coercivity mechanism in permanent magnets has been debated for many years.In this paper, various models of the coercivity mechanism are classified and re-examined by the comparison and contrast.Coherent rotation and curling models can reveal the underlying reversal mechanism clearly based on isolated grains with elliptic shapes.By contrast, the numerical methods consider inter-grain interactions while simulating the evolution of the spins and hysteresis loops with complicated shapes.However, an exact simulation of magnetic reversal in permanent nanomagnets requires many meshes to mimic the thin domain wall well.Nucleation and pinning are the two main coercivity mechanisms in permanent magnets.The former signifies the beginning of the magnetic reversal, whilst the latter completes it.Recently, it is proposed that the large difference between the intrinsic magnetic properties of the nucleation centers and those of the main phase can result in a large pinning field(self-pinning), which has the attributes of both traditional nucleation and pinning.Such a pinning explains the experimental data of permanent magnets very well, including the enhancement of the coercivity by the grain boundary pinning.

Functionalization of Cobalt Ferrite Nanoparticles with Alginate Coating for Biocompatible Applications

The soft magnetic materials have potential applications in the field of bioengineering as carriers for targeted drug delivery. The magnetic properties, particle size after coating, Curie temperature and its biocompatibility are important parameters for the synthesis of materials. In the present communication cobalt ferrite nanoparticles have been synthesized using co-precipitation method and coated with sodium alginate. The X-ray diffraction and infrared spectroscopic measurements have been used to confirm the ferrite structure formation and coating of the samples with alginate. The SEM micrographs have been used to confirm the particle size which is found to be 45 nm before coating and 78 nm after coating. The saturation magnetization obtained using the hysteresis data for the uncoated cobalt ferrite sample is 19.8 emu/gm while for the coated sample it reduces to 10.2 emu/gm. The AC susceptibility measurements indicate SP structure for the uncoated samples with Curie temperature less than 100℃. The thermo gravimetric measurements have been used to estimate the amount of alginate coating on the sample and it has been correlated with retention of magnetic properties after coating. The value of saturation magnetization reduces after coating due to mass reduction of magnetic material in the sample in accordance with the TGA measurements.

Nanomagnet-facilitated pharmaco-compatibility for cancer diagnostics:Underlying risks and the emergence of ultrasmall nanomagnets

Cancer therapy is a fast-emerging biomedical paradigm that elevates the diagnostic and therapeutic potential of a nanovector for identification,monitoring,targeting,and post-treatment response analysis.Nanovectors of superparamagnetic iron oxide nanoparticles(SPION)are of tremendous significance in cancer therapy because of their inherited high surface area,high reactivity,biocompatibility,superior contrast,and magnetic and photo-inducibility properties.In addition to a brief introduction,we summarize various progressive aspects of nanomagnets pertaining to their production with an emphasis on sustainable biomimetic approaches.Post-synthesis particulate and surface alterations in terms of pharmaco-affinity,liquid accessibility,and biocompatibility to facilitate cancer therapy are highlighted.SPION parameters including particle contrast,core-fusions,surface area,reactivity,photosensitivity,photodynamics,and photothermal properties,which facilitate diverse cancer diagnostics,are discussed.We also elaborate on the concept of magnetism to selectively focus chemotherapeutics on tumors,cell sorting,purification of bioentities,and elimination of toxins.Finally,while addressing the toxicity of nanomaterials,the advent of ultrasmall nanomagnets as a healthier alternative with superior properties and compatible cellular interactions is reviewed.In summary,these discussions spotlight the versatility and integration of multitasking nanomagnets and ultrasmall nanomagnets for diverse cancer theragnostics.

Calculation of Magnetic Configuration and Resistance for Nanomagnets

Based on a classical Heisenberg lattice model with dipole-dipole interaction and the method of spin dynamic simulation, the magnetic configurations (MC), hysteresis loops (HL) and magnetic resistance (MR) of the nanomagnets with different geometries, such as circle, square and rectangle, are studied for different directions of applied field. In the case of perpendicular field to the plane, the magnetization and MR are reversible and have not hysteresis. When the field is applied in the plane, the HL is irreversible and is qualitatively well agreeable with the current experimental results. The MR loop is also irreversible and appears two peaks distributed at two sides around zero field. The peaks of magnetic resistance are relative to the vortex state or similar configuration. Large easy-axis anisotropy will suppress the MC anisotropy, and the large magnetoresistance effect disappears.

Nanomagnetism:Principles,nanostructures,and biomedical applications

Nanomagnetism is the origin of many unique properties in magnetic nanomaterials that can be used as building blocks in information technology, spintronics, and biomedicine. Progresses in nanomagnetic principles, distinct magnetic nanostructures, and the biomedical applications of nanomagnetism are summarized.

Non-Abelian Geometric Manipulation of a Crystal of Molecular Nanomagnet Mn_(12)

Based on the strong magnetic anisotropy along the symmetry of the crystal, we construct a U（2） non-Abelian gauge potential for the molecular nanomagnet Mn12 by varying the external magnetic field adiabatically. Moreover, the non-Abelian geometric phase and the unitary matrix operation, which are tile key steps to realize the universal holonomic quantum computing in the degenerate subspace, are also obtained by means of choosing an evolution path properly.

Modification of Titanium Dioxide for Wastewater Treatment Application and Its Recovery for Reuse

Magnetic Fe3O4 nanomagnetic particles were synthesized by the titration co-precipitation method followed by coating by the sol-gel method with Titamiun dioxide. The photocalytic activities of different synthesized TiO2/Fe304 nanomagnetic particles with different molar ratios of TiO2 to Fe3O4 were investigated by the reduction of phosphate, nitrate and decolorizing of methyl blue solutions. X-ray diffraction was used to characterize the size, composition and morphology of the synthesized particles. The results obtained from these experiments indicate an increase in the photocatalytic activity as the amount of TiO2 coating increases. The results show a higher activity of the synthesized particles in the removal of phosphate, nitrate and methyl blue, which can be achieved at early reaction periods at about 70-80%. The activities were higher when the particles were incubated without UV illumination. This study shows that TiO2/Fe3O4 particles are effective in phosphate, nitrate and methyl blue removal in wastewater treatment.

Combining two-photon lithography with laser ablation of sacrificial layers:A route to isolated 3D magnetic nanostructures

Three-dimensional(3D)nanostructured functional materials are important systems allowing new means for intricate control of electromagnetic properties.A key problem is realising a 3D printing methodology on the nanoscale that can yield a range of functional materials.In this article,it is shown that two-photon lithography,when combined with laser ablation of sacrificial layers,can be used to realise such a vision and produce 3D functional nanomaterials of complex geometry.Proof-of-principle is first shown by fabricating planar magnetic nanowires raised above the substrate that exhibit controlled domain wall injection and propagation.Secondly,3D artificial spin-ice(3DASI)structures are fabricated,whose complex switching can be probed using optical magnetometry.We show that by careful analysis of the magneto-optical Kerr effect signal and by comparison with micromagnetic simulations,depth dependent switching information can be obtained from the 3DASI lattice.The work paves the way for new materials,which exploit additional physics provided by non-trivial 3D geometries.

Tailoring magnetic and electric resonances with dielectric nanocubes for broadband and high-efficiency unidirectional scattering

The interference of optically induced electric and magnetic resonances in high-refractive-index dielectric nanoparticles provides a new approach to control and shape the scattering patterns of light in the field of nanophotonics. In this Letter, we spectrally tune the electric and magnetic resonances by varying the geometry of a single isolated lead telluride （PbTe） dielectric nanocube. Then, we overlap the electric dipole resonance and magnetic dipole resonance to suppress backward scattering and enhance forward scattering in the resonance region. Furthermore, a broadband unidirectional scattering is achieved by structuring the dielectric nanocuboids as a trimer antenna.

A Unifi ed Geometric Rule for Designing Nanomagnetism in Graphene

Based on the underlying graphene lattice symmetry and an itinerant magnetism model on a bipartite lattice,we propose a unifi ed geometric rule for designing graphene-based magnetic nanostructures:spins are parallel(ferromagnetic(FM))on all zigzag edges which are at angles of 0°and 120°to each other,and antiparallel(antiferromagnetic(AF))at angles of 60°and 180°.The rule is found to be consistent with all the systems that have been studied so far.Applying the rule,we predict several novel graphene-based magnetic nanostructures:0-D FM nanodots with the highest possible magnetic moments,1-D FM nanoribbons,and 2-D magnetic superlattices.

Cube-octameric silsesquioxane (POSS)-capped magnetic iron oxide nanoparticles for the efficient removal of methylene blue

Octavinyl polyhedral oligomeric silsesquioxane (POSS) was polymerized on the surface of Fe3O4 nanoparticles (NPs) and then the NPs were functionalized with carboxylic acid groups using thiol-ene click reactions with thioglycolic acid.The as-prepared Fe3O4@POSS-COOH magnetic hybrid NPs had mesoporous structures with an average particle diameter of 15 nm and a relatively high specific surface area of 447 m^2· g^-1.Experimental results showed that 4 mg of Fe3O4@POSS-COOH NPs efficiently adsorbed and removed methylene blue from water at 5 min.This is due to the presence of both carboxylic acid and pendant vinyl groups on the Fe3O4@POSS-COOH NPs.These NPs could be easily withdrawn from water within a few seconds under moderate magnetic field and showed high stability in acid and alkaline aqueous mediums.

Nanomagnetic Organogel Based on Dodecyl Methacrylate for Absorption and Removal of Organic Solvents

A novel nanomagnetic organogel was synthesized by in situ emulsion polymerization-crosslinking method using dodecyl methacrylate(DDMA) and styrene(St) as monomers, divinylbenzene(DVB) as a crosslinking agent, azobisisobutyronitrile(AIBN) as an initiator, and Fe_3O_4 as a nanomagnetic particle. Modification of the network was carried out by inclusion of the multi-walled carbon nanotubes(MWCNT) into the organogel matrix. The structure of the nanocomposite was characterized using FTIR spectroscopy, SEM,TEM, TGA/DTG, VSM, and BET analysis. The effects of various parameters such as the amount of crosslinker, initiator, Fe_3O_4, and reaction time as well as monomer ratio on the oil absorption of the organogel were studied. The synthesized organogel can absorb about35.5, 22.1, 29.86, 14.58, 17.6, 15.3, and 13.7 g·g^(-1) of CHCl_3, toluene, CH_2Cl_2, hexane, crude oil, gasoline, and diesel oil, under the optimized polymerization conditions, respectively. The nanocomposite organogels can be easily separated by a magnetic field after absorption of organic solvents.

Nonreciprocal coherent coupling of nanomagnets by exchange spin waves

Nanomagnets are widely used to store information in non-volatile spintronic devices.Spin waves can transfer information with low-power consumption as their propagations are independent of charge transport.However,to dynamically couple two distant nanomagnets via spin waves remains a major challenge for magnonics.Here we experimentally demonstrate coherent coupling of two distant Co nanowires by fast propagating spin waves in an yttrium iron garnet thin film with sub-50 nm wavelengths.Magnons in two nanomagnets are unidirectionally phase-locked with phase shifts controlled by magnon spin torque and spin-wave propagation.The coupled system is finally formulated by an analytical theory in terms of an effective non-Hermitian Hamiltonian.Our results are attractive for analog neuromorphic computing that requires unidirectional information transmission.

Composition- and oxidation-controlled magnetism ternary FeCoNi nanocrystals

Ternary FeCoNi metallic nanostructures have attracted significant attention due to their high saturation magnetization, unique mechanical properties, and large corrosion resistance. In this study, we report a controlled synthesis of ternary FeCoNi nanocrystals using solution-based epitaxial core-shell nanotechnology. The thickness and stoichiometry of the FeCoNi nanocrystals affect their magnetic characteristics, which can be controlled by a phase transformation-induced tetragonal distortion. Furthermore, surface oxidation of the stoichiometry-controlled FeCoNi nanostructures can drastically enhance their magnetic coercivity （up to 8,881.60e for AuCu-FeCo）, and optimize the AuCu-FeCo08Ni0.2 performance corresponding to the saturated magnetization of 134.4 emu-g-1 and coercivity of 4,036.70e, which opens the possibility of developing rare-earth free high energy nanomagnets.

Ferritin surplus in mouse spleen 14 months after intravenous injection of iron oxide nanoparticles at clinical dose

In this study, we followed the biodegradation of ultra-small superparamagnetic iron oxide nanoparticles injected intravenously at clinical doses in mice. An advanced fitting procedure for magnetic susceptibility curves and low- temperature hysteresis loops was used to fully characterize the magnetic size distribution as well as the magnetic anisotropy energy of the injected P904 nano- particles （Guerbet Laboratory）. Additional magnetometry measurements and transmission electronic microscopy observations were systematically performed to examine dehydrated samples from the spleen and liver of healthy C57B16 mice after nanoparticle injection, with sacrifice of the mice for up to 14 months. At 3 months after injection, the magnetic properties of the spleen and liver were dramatically different. While the liver showed no magnetic signals other than those also present in the reference species, the spleen showed an increased magnetic signal attributed to ferritin. This surplus of ferritin remained constant up to 14 months after injection.

Reliability analysis of magnetic logic interconnect wire subjected to magnet edge imperfections

Nanomagnet logic（NML） devices have been proposed as one of the best candidates for the next generation of integrated circuits thanks to its substantial advantages of nonvolatility, radiation hardening and potentially low power. In this article, errors of nanomagnetic interconnect wire subjected to magnet edge imperfections have been evaluated for the purpose of reliable logic propagation. The missing corner defects of nanomagnet in the wire are modeled with a triangle, and the interconnect fabricated with various magnetic materials is thoroughly investigated by micromagnetic simulations under different corner defect amplitudes and device spacings. The results show that as the defect amplitude increases, the success rate of logic propagation in the interconnect decreases. More results show that from the interconnect wire fabricated with materials, iron demonstrates the best defect tolerance ability among three representative and frequently used NML materials, also logic transmission errors can be mitigated by adjusting spacing between nanomagnets. These findings can provide key technical guides for designing reliable interconnects.

magnetic tunnel junctions spin-transfer torque magneto-resistance nanomagnet dynamics

We investigate bias and different barrier thicknesses effects on quantities related to spin and charge currents in MgO-based magnetic tunnel junctions. Using the non-Equilibrium Green＇s function formalism, we demonstrate that the in-plane and out-of-plane components of the spin-transfer torque have asymmetric and symmetric behaviors respectively. Magneto-resistance also decreases with increasing barrier thickness. The Landau–Lifshits–Gilbert equation describes the dynamics of the magnetization made by spin transfer torque. Increasing in spin current above its critical value or smaller the magnet reduces the switching time which is major result for making of new memory devices.

Highly efficient and regioselective thiocyanation of aromatic amines,anisols and activated phenols with H_2O_2/NH_4SCN catalyzed by nanomagnetic Fe_3O_4

A new method employing magnetic nanoparticles Fe3O4 as a catalyst and H2O2 as a green oxidant is developed for the oxidative thiocyanation of aromatic amines, anisols and activated phenols with high yields under mild reaction conditions. The catalyst could be easily recovered from the reaction mixture using an external magnet and reused in several reaction cycles without loss of activity.