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, disti...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.展开更多
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(fe...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.展开更多
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 c...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.展开更多
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, azobisis...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.展开更多
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 biocompati...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.展开更多
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 ...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.展开更多
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 nanom...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.展开更多
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. More...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.展开更多
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 TiO...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.展开更多
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 demonst...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.展开更多
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 ...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.展开更多
Lanthanide single-molecule magnets(Ln-SMMs)have attracted scientific attention due to their potential application in data storage and spintronics.On the other hand,stimuli-responsive molecular materials are considered...Lanthanide single-molecule magnets(Ln-SMMs)have attracted scientific attention due to their potential application in data storage and spintronics.On the other hand,stimuli-responsive molecular materials are considered for chemical sensors thanks to their solvato-and vapochromism.Aiming at advanced multifunctionality,the Ln-SMMs can be functionalized toward various physical properties,e.g.,luminescence or ferroelectricity.We present an approach toward the conjunction of molecular nanomagnetism with solvatochromism in solution and vapochromism in the solid state.Our concept is based on combining Dy^(III)complexes bearing O-donor ligands,i.e.,4-pyridone(4-pyone),responsible for the SMM property,with dicyanido-bis(1,10-phenanthroline)iron(II)metalloligands inducing a chemochromic response.We report tetranuclear molecules,{[Dy^(III)(4-pyone)_(5)]_(2)[Fe^(II)(CN)_(2)(phen)_(2)]_(2)}(CF_(3)SO_(3))_(6)(1)containing(4-pyone)-bridged{Dy^(III)2}6+units which exhibit pronounced SMM characteristics due to the axial alignment of 4-pyone ligands within a pentagonal bipyramidal geometry and the weakening of quantum tunneling of magnetization(QTM)achieved by ligand-mediated exchange coupling.The{Dy^(III)_(2)}SMMs are cyanidobridged to Fe^(II)complexes and the resulting{Dy^(III)2 Fe^(II)_(2)}^(6+)cations could be dissolved in various solvents providing distinct solvatochromism achieved by tunable charge-transfer absorption of dicyanidometallates.The optical sensitivity of 1 to solvent molecules was also found in the solid state unveiling efficient vapochromism related to the incorporation of solvent vapors into the crystals of 1.The variously solvated phases of 1 were isolated from alcohol solutions giving a series of compounds,namely 1·MeOH,1·EtOH,1·PrOH,and 1·BuOH,differing not only in light absorption but also in SMM features,including the level of quenching of the QTM.展开更多
Lanthanide molecular nanomagnets featuring reversible photoresponsive characteristics and photomediated magnetic behavior are highly appealing for developing next-generation optics and memory devices though the ration...Lanthanide molecular nanomagnets featuring reversible photoresponsive characteristics and photomediated magnetic behavior are highly appealing for developing next-generation optics and memory devices though the rational assembly of such materials remains elusive.Herein,we demonstrate a stepwise approach,which employs a photochromic dysprosium-viologen compound{[Dy(ipbp)_(2)(H_(2)O)3]·NO_(3)·2H_(2)O}n(1)(H_(2)ipbp·Cl=(1-(3,5-dicarboxyphenyl)-4,4’-bipyridinium chloride))as the building block and 2,5-pyrazinedicarboxylate dianions(2,5-pzdc2-)as bridges,giving rise to a new framework{[Dy(ipbp)_(2)(2,5-pzdc)0.5(H_(2)O)]·5H_(2)O}n(2)exhibiting a photochromic effect and slow magnetic relaxation under a zero dc field.This finding is notable and exciting,as the starting compound 1 shows no magnetic relaxation on its own.The ab initio calculations demonstrate that by replacing water molecules at the equatorial plane in 1 with the 2,5-pzdc2-bridge,the longer Dy-N bond length and the less charged pyrazine nitrogen atom result in a weaker equatorial field strength,and the coordination geometry around the Dy^(3+)ion in 2 is thus closer to the ideal triangular dodecahedral geometry than in 1,leading to stronger axial magnetic anisotropy of the Dy^(3+)ion and switch-on of slow magnetic relaxation under a zero dc field.Further magnetic analysis of compound 2 before and after UV light irradiation reveals the weak ferromagnetic coupling between the photogenerated radicals and the Dy^(3+)ions,a slight inhibition of quantum tunnelling of magnetization,as well as a modest enhancement of the energy barrier for the slow magnetic relaxation,highlighting the photomodulation of the dynamic magnetic behavior.展开更多
The self-assembly of lanthanide(3+)ions with pyrazine N,N′-dioxide(pzdo)and bis(triphenylphosphine)iminium(PPN+)salts of diamagnetic octacyanidometallates of MoIV and WIV results in one-dimensional(PPN)[LnIII(pzdo)2(...The self-assembly of lanthanide(3+)ions with pyrazine N,N′-dioxide(pzdo)and bis(triphenylphosphine)iminium(PPN+)salts of diamagnetic octacyanidometallates of MoIV and WIV results in one-dimensional(PPN)[LnIII(pzdo)2(MeOH)0.3(H2O)3.7][MIV(CN)8]·7.7H2O·2MeOH(Ln=Er and Yb;M=Mo and W)coordination networks.They are constructed of zigzag metal–organic{LnIII(μ-pzdo)}n chains with terminal[MIV(CN)8]4−metalloligands attached to the LnIII centres.Both Er-and Yb-containing frameworks exhibit field-induced slow magnetic relaxation originating from the field-dependent equilibrium between quantum tunnelling of magnetization and the direct process along with the temperature-dependent Raman and Orbach relaxation processes.Transition metal substitution on[MIV(CN)8]4−sites modifies the intrinsic magnetic anisotropy of lanthanides,as depicted by the subtle change of thermal energy barriers of Orbach relaxation in Er-based systems,while it significantly affects Raman relaxation due to the modulated phonon mode scheme.All reported compounds exhibit strong visible light absorption due to a series of electronic transitions of pzdo ligands and[M(CN)8]4−ions and the appearance of low energy anion–π charge transfer band involving pzdo and octacyanidometallates.These charge transfer states were utilized in achieving the sensitized near-infrared photoluminescence of Er^(Ⅲ) and Yb^(Ⅲ) centers;thus,the energy transfer process is strongly dependent on the nature of the metal centre in the[M^(Ⅳ)(CN)8]4−ion.The W(Ⅳ)-pzdo system is a good sensitizer for Er^(Ⅲ),while the Mo(Ⅳ)-pzdo unit is better for Yb^(Ⅲ) emission which can be rationalized in terms of the positions of energy levels of their respective donor states.Therefore,we report NIR emissive Er^(Ⅲ) and Yb^(Ⅲ) single-molecule magnets with tunable magnetic and optical properties,uncovering the crucial role of octacyanidometallates and their anion–π interactions with pzdo ligands.展开更多
Lanthanide(Ⅲ)single-molecule magnets(SMMs)are a tool for the combination of molecular nanomagnetism with luminescent thermometry,opening the pathway not only for broadened multifunctionality but also for the optical ...Lanthanide(Ⅲ)single-molecule magnets(SMMs)are a tool for the combination of molecular nanomagnetism with luminescent thermometry,opening the pathway not only for broadened multifunctionality but also for the optical self-monitoring of temperature in SMM-based systems.Usually,this goal is realized by exploring the intrinsic properties of a single lanthanide(Ln)ion.We present an innovative strategy based on embedding magnetically anisotropic Ln(Ⅲ)centers into a red-emissive coordination system based on Eu(Ⅲ)complexes of a nonmagnetic ground state.This concept is presented for novel cyanido-bridged chains,{[LnⅢ(dppmO_(2))_(3)][AgI(CN)_(2)]}[OTf]_(2)(Ln=Eu,EuAg;Ln=Er,ErAg;Ln=Yb,YbAg;Ln=Er_(0.05)Eu_(0.95),Er@EuAg;Ln=Yb_(0.04)Eu_(0.96),Yb@EuAg;dppmO_(2)=bis(diphenylphosphino)methane dioxide;OTf=trifluoromethanesulfonate).The Ln(Ⅲ)coordination sphere,consisting of O,O-bidentate dppmO_(2) ligands occupying the equatorial positions and two axially aligned cyanido bridges,generates the distinct SMM characteristics of Er(Ⅲ)/Yb(Ⅲ)centers.Alternatively,the strong photoluminescence of Eu(Ⅲ)in EuAg exhibits pronounced thermal variation of the excitation spectrum,which is employed for ratiometric optical thermometry,revealing a relative thermal sensitivity(Sr)of up to 2.1%K^(−1) at 55 K and a good thermometric response below 110 K.The incorporation of Er(Ⅲ)/Yb(Ⅲ)centers into the Eu(Ⅲ)-based framework leads to heterotrimetallic Er@EuAg and Yb@EuAg systems,which link the SMM features with luminescent thermometry.Both physical properties are enhanced upon mixing of the Ln(Ⅲ)centers,as depicted by the slowdown of magnetic relaxation,especially for Er(Ⅲ),due to the Eu(Ⅲ)-induced weakening of the quantum tunneling of magnetization,which is accompanied by the improved thermometric response,including an increase in the maximal Sr to 3.3%K^(−1) and broadening of its operating range to 150 K,due to the structural distortion induced by Er(Ⅲ)/Yb(Ⅲ)centers.展开更多
The development of single-chain magnets with reversible and adjustable properties is of great significance for achieving high-density information storage and switching devices with multi-stimuli responsiveness,but it ...The development of single-chain magnets with reversible and adjustable properties is of great significance for achieving high-density information storage and switching devices with multi-stimuli responsiveness,but it remains a challenging task.In this work,we synthesized a new cyano-bridged{Fe_(2)Co}-based coordination polymer,{[(PzTp)Fe(CN)_(3)]_(2)Co(Ipi)_(2)}·2MeOH·0.5H_(2)O(1·solv;^(pz)Tp,tetra-kis(1-pyrazolyl)borate;Ipi,1-(4-iodophenyl)-1H-imidazole).1·solv displayed reversible metal-to-metal electron transfer(MMET)between FeIII LS(μ-CN)CoII HS(μ-NC)Fe_(LS)^(III)(LS,low spin;HS,high spin)and Fe_(LS)^(III)(μ-CN)Co^_(LS)^(III)(μ-NC)FeII LS states under alternating irradiations with 808 and 532 nm lasers,respectively,as verified by photomagnetic and in situ photo-monitored X-ray diffraction studies.The bidirectional light irradiations induced significant changes in magnetic anisotropy and intrachain exchange interactions,demonstrating the on/off switching of single-chain magnet(SCM)behavior by 808 and 532 nm light irradiations.1·solv underwent a thermally induced single-crystal-to-single-crystal(SCSC)phase transition into a desolvated{[(^(Pz)Tp)Fe(CN)_(3)]_(2)Co(Ipi)_(2)}(1·desolv)phase,accompanying MMET.Magnetic susceptibility measurements indicated that 1·desolv exhibited thermally induced incomplete MMET behavior and field-induced nanomagnet behavior.1·desolv also displayed a substantial dielectric anomaly during the electron transfer process,presenting a new case showing the synergetic switching of the dielectric and magnetic properties.Interestingly,1·desolv can revert to the solvated phase 1·resolv after being soaked in mother liquor,whose SCM behavior was erased by the reversible SCSC transition.This study provides a new approach for the swift and reversible control of SCM behavior via both SCSC transition and light-induced MMET.展开更多
Professor Song Gao,Editor-in-Chief Professor Song Gao is Professor of Inorganic Chemistry at Peking University(PKU),China.His research interests are magnetic ordered coordination polymers,molecular nanomagnets,molecul...Professor Song Gao,Editor-in-Chief Professor Song Gao is Professor of Inorganic Chemistry at Peking University(PKU),China.His research interests are magnetic ordered coordination polymers,molecular nanomagnets,molecular and crystal engineering,and multifunctional molecular materials.He was a Humboldt Research Fellow at TH Aachen from 1995 to 1997.展开更多
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 controll...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.展开更多
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 nanosca...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.展开更多
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 curve...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.展开更多
基金Project supported by the National Basic Research Program of China(Grant No.2010CB934601)the National Natural Science Foundation of China(Grant Nos.51125001 and 51172005)+1 种基金the Natural Science Foundation of Beijing,China(Grant No.2122022)the Doctoral Program,China(Grant No.20120001110078)
文摘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.
基金The work at Utah is supported by DOEthe work at IOP is supported by NSFC+1 种基金the work at UoW is supported by the Australian Research Council(ARC)Discovery grantLiu also acknowledges support by an ARC international professorial fellowship and Dr.X.L.Wang for helping to prepare the figures.First principles calculations were performed on computers at DOE-NERSC and CHPC of University of Utah.
文摘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.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11074179,51771127,51571126,and 51772004)the Scientific Research Fund of Sichuan Provincial Education Department,China(Grant Nos.18TD0010 and 16CZ0006)
文摘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.
文摘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.
文摘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.
基金Department of Science and Technology,Government of India,NewDelhi,for financial support through Early Career Research Award(Grant No.:ECR/2017/000339).
文摘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.
文摘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.
基金Supported by the National Natural Science Foundation of China under Grant Nos. 11074154, 11074184, and 11075099the National Science Funding of Zhejiang Province under Grant No. Y6090001
文摘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.
文摘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.
文摘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.
基金financial support of this study by Shiraz University Research Council
文摘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.
基金financed by the National Science Center of Poland,the OPUS-21 project(2021/41/B/ST5/02544)。
文摘Lanthanide single-molecule magnets(Ln-SMMs)have attracted scientific attention due to their potential application in data storage and spintronics.On the other hand,stimuli-responsive molecular materials are considered for chemical sensors thanks to their solvato-and vapochromism.Aiming at advanced multifunctionality,the Ln-SMMs can be functionalized toward various physical properties,e.g.,luminescence or ferroelectricity.We present an approach toward the conjunction of molecular nanomagnetism with solvatochromism in solution and vapochromism in the solid state.Our concept is based on combining Dy^(III)complexes bearing O-donor ligands,i.e.,4-pyridone(4-pyone),responsible for the SMM property,with dicyanido-bis(1,10-phenanthroline)iron(II)metalloligands inducing a chemochromic response.We report tetranuclear molecules,{[Dy^(III)(4-pyone)_(5)]_(2)[Fe^(II)(CN)_(2)(phen)_(2)]_(2)}(CF_(3)SO_(3))_(6)(1)containing(4-pyone)-bridged{Dy^(III)2}6+units which exhibit pronounced SMM characteristics due to the axial alignment of 4-pyone ligands within a pentagonal bipyramidal geometry and the weakening of quantum tunneling of magnetization(QTM)achieved by ligand-mediated exchange coupling.The{Dy^(III)_(2)}SMMs are cyanidobridged to Fe^(II)complexes and the resulting{Dy^(III)2 Fe^(II)_(2)}^(6+)cations could be dissolved in various solvents providing distinct solvatochromism achieved by tunable charge-transfer absorption of dicyanidometallates.The optical sensitivity of 1 to solvent molecules was also found in the solid state unveiling efficient vapochromism related to the incorporation of solvent vapors into the crystals of 1.The variously solvated phases of 1 were isolated from alcohol solutions giving a series of compounds,namely 1·MeOH,1·EtOH,1·PrOH,and 1·BuOH,differing not only in light absorption but also in SMM features,including the level of quenching of the QTM.
基金supported by the National Natural Science Foundation of China(no.21671024 and 22271020).
文摘Lanthanide molecular nanomagnets featuring reversible photoresponsive characteristics and photomediated magnetic behavior are highly appealing for developing next-generation optics and memory devices though the rational assembly of such materials remains elusive.Herein,we demonstrate a stepwise approach,which employs a photochromic dysprosium-viologen compound{[Dy(ipbp)_(2)(H_(2)O)3]·NO_(3)·2H_(2)O}n(1)(H_(2)ipbp·Cl=(1-(3,5-dicarboxyphenyl)-4,4’-bipyridinium chloride))as the building block and 2,5-pyrazinedicarboxylate dianions(2,5-pzdc2-)as bridges,giving rise to a new framework{[Dy(ipbp)_(2)(2,5-pzdc)0.5(H_(2)O)]·5H_(2)O}n(2)exhibiting a photochromic effect and slow magnetic relaxation under a zero dc field.This finding is notable and exciting,as the starting compound 1 shows no magnetic relaxation on its own.The ab initio calculations demonstrate that by replacing water molecules at the equatorial plane in 1 with the 2,5-pzdc2-bridge,the longer Dy-N bond length and the less charged pyrazine nitrogen atom result in a weaker equatorial field strength,and the coordination geometry around the Dy^(3+)ion in 2 is thus closer to the ideal triangular dodecahedral geometry than in 1,leading to stronger axial magnetic anisotropy of the Dy^(3+)ion and switch-on of slow magnetic relaxation under a zero dc field.Further magnetic analysis of compound 2 before and after UV light irradiation reveals the weak ferromagnetic coupling between the photogenerated radicals and the Dy^(3+)ions,a slight inhibition of quantum tunnelling of magnetization,as well as a modest enhancement of the energy barrier for the slow magnetic relaxation,highlighting the photomodulation of the dynamic magnetic behavior.
基金financed by the National Science Centre,Poland,within the OPUS-15 project,grant no.2018/29/B/ST5/00337supported by the Japan Society for the Promotion of Science,the Grant-in-Aid for Specially Promoted Research,grant no.15H05697.
文摘The self-assembly of lanthanide(3+)ions with pyrazine N,N′-dioxide(pzdo)and bis(triphenylphosphine)iminium(PPN+)salts of diamagnetic octacyanidometallates of MoIV and WIV results in one-dimensional(PPN)[LnIII(pzdo)2(MeOH)0.3(H2O)3.7][MIV(CN)8]·7.7H2O·2MeOH(Ln=Er and Yb;M=Mo and W)coordination networks.They are constructed of zigzag metal–organic{LnIII(μ-pzdo)}n chains with terminal[MIV(CN)8]4−metalloligands attached to the LnIII centres.Both Er-and Yb-containing frameworks exhibit field-induced slow magnetic relaxation originating from the field-dependent equilibrium between quantum tunnelling of magnetization and the direct process along with the temperature-dependent Raman and Orbach relaxation processes.Transition metal substitution on[MIV(CN)8]4−sites modifies the intrinsic magnetic anisotropy of lanthanides,as depicted by the subtle change of thermal energy barriers of Orbach relaxation in Er-based systems,while it significantly affects Raman relaxation due to the modulated phonon mode scheme.All reported compounds exhibit strong visible light absorption due to a series of electronic transitions of pzdo ligands and[M(CN)8]4−ions and the appearance of low energy anion–π charge transfer band involving pzdo and octacyanidometallates.These charge transfer states were utilized in achieving the sensitized near-infrared photoluminescence of Er^(Ⅲ) and Yb^(Ⅲ) centers;thus,the energy transfer process is strongly dependent on the nature of the metal centre in the[M^(Ⅳ)(CN)8]4−ion.The W(Ⅳ)-pzdo system is a good sensitizer for Er^(Ⅲ),while the Mo(Ⅳ)-pzdo unit is better for Yb^(Ⅲ) emission which can be rationalized in terms of the positions of energy levels of their respective donor states.Therefore,we report NIR emissive Er^(Ⅲ) and Yb^(Ⅲ) single-molecule magnets with tunable magnetic and optical properties,uncovering the crucial role of octacyanidometallates and their anion–π interactions with pzdo ligands.
基金the National Science Center of Poland,the OPUS-21 project(2021/41/B/ST5/02544).
文摘Lanthanide(Ⅲ)single-molecule magnets(SMMs)are a tool for the combination of molecular nanomagnetism with luminescent thermometry,opening the pathway not only for broadened multifunctionality but also for the optical self-monitoring of temperature in SMM-based systems.Usually,this goal is realized by exploring the intrinsic properties of a single lanthanide(Ln)ion.We present an innovative strategy based on embedding magnetically anisotropic Ln(Ⅲ)centers into a red-emissive coordination system based on Eu(Ⅲ)complexes of a nonmagnetic ground state.This concept is presented for novel cyanido-bridged chains,{[LnⅢ(dppmO_(2))_(3)][AgI(CN)_(2)]}[OTf]_(2)(Ln=Eu,EuAg;Ln=Er,ErAg;Ln=Yb,YbAg;Ln=Er_(0.05)Eu_(0.95),Er@EuAg;Ln=Yb_(0.04)Eu_(0.96),Yb@EuAg;dppmO_(2)=bis(diphenylphosphino)methane dioxide;OTf=trifluoromethanesulfonate).The Ln(Ⅲ)coordination sphere,consisting of O,O-bidentate dppmO_(2) ligands occupying the equatorial positions and two axially aligned cyanido bridges,generates the distinct SMM characteristics of Er(Ⅲ)/Yb(Ⅲ)centers.Alternatively,the strong photoluminescence of Eu(Ⅲ)in EuAg exhibits pronounced thermal variation of the excitation spectrum,which is employed for ratiometric optical thermometry,revealing a relative thermal sensitivity(Sr)of up to 2.1%K^(−1) at 55 K and a good thermometric response below 110 K.The incorporation of Er(Ⅲ)/Yb(Ⅲ)centers into the Eu(Ⅲ)-based framework leads to heterotrimetallic Er@EuAg and Yb@EuAg systems,which link the SMM features with luminescent thermometry.Both physical properties are enhanced upon mixing of the Ln(Ⅲ)centers,as depicted by the slowdown of magnetic relaxation,especially for Er(Ⅲ),due to the Eu(Ⅲ)-induced weakening of the quantum tunneling of magnetization,which is accompanied by the improved thermometric response,including an increase in the maximal Sr to 3.3%K^(−1) and broadening of its operating range to 150 K,due to the structural distortion induced by Er(Ⅲ)/Yb(Ⅲ)centers.
基金supported by the National Natural Science Foundation of China(Grants 22222103,22025101,22173015,22103009)the Fundamental Research Funds for the Central Universities(DUT22LAB606),China.
文摘The development of single-chain magnets with reversible and adjustable properties is of great significance for achieving high-density information storage and switching devices with multi-stimuli responsiveness,but it remains a challenging task.In this work,we synthesized a new cyano-bridged{Fe_(2)Co}-based coordination polymer,{[(PzTp)Fe(CN)_(3)]_(2)Co(Ipi)_(2)}·2MeOH·0.5H_(2)O(1·solv;^(pz)Tp,tetra-kis(1-pyrazolyl)borate;Ipi,1-(4-iodophenyl)-1H-imidazole).1·solv displayed reversible metal-to-metal electron transfer(MMET)between FeIII LS(μ-CN)CoII HS(μ-NC)Fe_(LS)^(III)(LS,low spin;HS,high spin)and Fe_(LS)^(III)(μ-CN)Co^_(LS)^(III)(μ-NC)FeII LS states under alternating irradiations with 808 and 532 nm lasers,respectively,as verified by photomagnetic and in situ photo-monitored X-ray diffraction studies.The bidirectional light irradiations induced significant changes in magnetic anisotropy and intrachain exchange interactions,demonstrating the on/off switching of single-chain magnet(SCM)behavior by 808 and 532 nm light irradiations.1·solv underwent a thermally induced single-crystal-to-single-crystal(SCSC)phase transition into a desolvated{[(^(Pz)Tp)Fe(CN)_(3)]_(2)Co(Ipi)_(2)}(1·desolv)phase,accompanying MMET.Magnetic susceptibility measurements indicated that 1·desolv exhibited thermally induced incomplete MMET behavior and field-induced nanomagnet behavior.1·desolv also displayed a substantial dielectric anomaly during the electron transfer process,presenting a new case showing the synergetic switching of the dielectric and magnetic properties.Interestingly,1·desolv can revert to the solvated phase 1·resolv after being soaked in mother liquor,whose SCM behavior was erased by the reversible SCSC transition.This study provides a new approach for the swift and reversible control of SCM behavior via both SCSC transition and light-induced MMET.
文摘Professor Song Gao,Editor-in-Chief Professor Song Gao is Professor of Inorganic Chemistry at Peking University(PKU),China.His research interests are magnetic ordered coordination polymers,molecular nanomagnets,molecular and crystal engineering,and multifunctional molecular materials.He was a Humboldt Research Fellow at TH Aachen from 1995 to 1997.
基金S. R. thanks the financial support from the U.S. National Science Foundation （NSF） （No. NSF-DMR-1551948） （magnetically hard nanocrystals） and （No. NSF- CMMI-1553986） （nanomanufacturing）.
文摘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.
基金S.L.acknowledges funding from the Engineering and Physics Research Council(EP/R009147/1)from the Leverhulme Trust(RPG-2021-139).
文摘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.
文摘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.
