Two new 3D pillared-layer cobalt(II)molecular magnetic materials,formulated as{[Co_(2)(TDA)(TZ)-(H_(2)O)_(2)]·H_(2)O}n(1)and{[Co_(3)(TDA)_(2)(bpy)_(3)]·6.75H_(2)O}_(n)(2)(H_(3)TDA=1H-1,2,3-triazole-4,5-dicar...Two new 3D pillared-layer cobalt(II)molecular magnetic materials,formulated as{[Co_(2)(TDA)(TZ)-(H_(2)O)_(2)]·H_(2)O}n(1)and{[Co_(3)(TDA)_(2)(bpy)_(3)]·6.75H_(2)O}_(n)(2)(H_(3)TDA=1H-1,2,3-triazole-4,5-dicarboxylic acid,HTZ=1H-1,2,4-triazole and bpy=4,4’-bipyridine),have been successfully assembled with H_(3)TDA and auxiliary ligands,respectively.展开更多
The anomalous Nernst effect(ANE),which enables energy conversion and harvesting in ferromagnetic materials through orthogonal charge generation relative to the heat gradient and magnetization,holds great promise for s...The anomalous Nernst effect(ANE),which enables energy conversion and harvesting in ferromagnetic materials through orthogonal charge generation relative to the heat gradient and magnetization,holds great promise for spintronic thermoelectric applications.However,achieving both perpendicular magnetic anisotropy(PMA)and an out-of-plane thermal gradient—two essential prerequisites for highly stable and efficient spintronic devices—contradicts the orthogonality condition required for ANE generation.In this study,we leverage the novel spincanting effect in ferrimagnetic CoTb films to realize a pronounced ANE response near the magnetic compensation temperature,yielding a remarkable ANE coefficient of 0.108μV/K.By further investigating the angular characteristics of the spin-canted state,we optimize and identify the ideal measurement scheme for spin-canting-mediated ANE.Our findings systematically elucidate the unique physical behavior of this unconventional ANE and demonstrate the potential of ferrimagnetic systems with strong PMA for developing high-performance thermoelectric devices.展开更多
By using the derivative method, we obtained the same result with that of the previous work of Chen et al. in 2006. Different from the integral form, the derivative form of the surface expression published in this pape...By using the derivative method, we obtained the same result with that of the previous work of Chen et al. in 2006. Different from the integral form, the derivative form of the surface expression published in this paper is derived from differential equation and based on the theory of non-imaging focusing heliostat proposed by Chen et al. in 2001. The comparison of the derivative form of fixed aberration correction surface has been made with that of integral form surface as well as that of spherical surface in concentrating the solar ray.展开更多
Based on the bent ligand 1 H-3-(3-pyridyl)-5-(4-pyridyl)-1,2,4-triazole(3,4?-Hbpt) with Co(Ⅱ) ions as well as a series of polycarboxylate co-ligands, three new coordination polymers were yielded, namely, {[Co(op)(3,4...Based on the bent ligand 1 H-3-(3-pyridyl)-5-(4-pyridyl)-1,2,4-triazole(3,4?-Hbpt) with Co(Ⅱ) ions as well as a series of polycarboxylate co-ligands, three new coordination polymers were yielded, namely, {[Co(op)(3,4?-Hbpt)(H_2O)_3]?2 H_2O}n(1), [Co(cyc)(3,4′-Hbpt)(H_2O)]n(2) and [Co(pro)(3,4′-Hbpt)(H_2O)]n(3)(here, op = o-phthalic anion, cyc = 1,1-cyclobutanedicarboxylic anion, pro = propanedioic anion). In cooperation with the auxiliary polycarboxylate co-ligands, a variety of Co(Ⅱ) coordination networks, such as 1-D chain 1 and 2-D layer 2 and 3 have been assembled. The magnetic behaviors of compounds 1～3 were studied. All of them indicated the existence of interesting spin-canting behavior.展开更多
A new three-dimensional nickel（Ⅱ） hydrogen-bonded molecular self assembly containing [（Ni（nicotinamide）2（thiocyanate）2（H2O）2] complex has been synthesized and characterized by single-crystal X-ray diffractio...A new three-dimensional nickel（Ⅱ） hydrogen-bonded molecular self assembly containing [（Ni（nicotinamide）2（thiocyanate）2（H2O）2] complex has been synthesized and characterized by single-crystal X-ray diffraction,FTIR spectroscopy,thermal analysis and magnetic measurements.Structural analysis reveals that the complex crystallizes in triclinic space group P1（crystal data a = 7.5574,b = 8.2683,c = 9.0056 A,α = 73.010,β = 69.698,γ = 66.51） and exhibits a distorted octahedral coordination sphere.Most interesting point in its structure is the involvement of sulphur atom of thiocyanate moiety in the trifurcated hydrogen bonding to build up the hydrogen-bonded self assembly.The magnetic behavior as determined by squid magnetometer（2~300 K temp.range） reveals dominating antiferromagnetic interaction followed by spin canting behavior below 20 K.展开更多
It is the result of a systemic study about uniform hematite nanopallets with length of about 100 nm, width of about 30 nm, and thickness of less than 10 nm. The sample has superparamagnetic(SPM) properties above the b...It is the result of a systemic study about uniform hematite nanopallets with length of about 100 nm, width of about 30 nm, and thickness of less than 10 nm. The sample has superparamagnetic(SPM) properties above the blocking temperature of ～16 K. The temperature dependence of magnetization was well fitted by Bloch T^(3/2) law considering the dipolar interaction of the particles. The field dependence of magnetization was fitted with revised Langevin equation.The magnetization of the weak ferromagnetic(WF) canted spins contributes to the linear portion in the high field region;the surface uncompensated spins and the parasitic ferromagnetic moments due to the canted spins both contribute to the particle moments and the superparamagnetic behavior.展开更多
The Heisenberg-Kitaev(HK)model on various lattices has attracted a lot of attention because it may lead to exotic states such as quantum spin liquid and topological orders.The rare-earth-based kagome lattice(KL)compou...The Heisenberg-Kitaev(HK)model on various lattices has attracted a lot of attention because it may lead to exotic states such as quantum spin liquid and topological orders.The rare-earth-based kagome lattice(KL)compounds Mg_(2)RE_(3)Sb_(3)O_(14)(RE=Gd,Er)and(RE=Nd)have q=0,120°order and canted ferromagnetic(CFM)order,respectively.Interestingly,the HK model on the KL has the same ground state long-range orders.In the theoretical phase diagram,the CFM phase resides in a continuous parameter region and there is no phase change across special parameter points,such as the Kitaev ferromagnetic(KFM)point,the ferromagnetic(FM)point and its dual FM point.However,a ground state property cannot distinguish a system with or without topological nontrivial excitations and related phase transitions.Here,we study the topological magnon excitations and related thermal Hall conductivity in the HK model on the KL with CFM order.The CFM phase can be divided into two regions related by the Klein duality,with the self dual KFM point as their boundary.We find that the scalar spin chirality,which is intrinsic in the CFM order,changes sign across the KFM point.This leads to the opposite Chem numbers of corresponding magnon bands in the two regions,and also the sign change of the magnon thermal Hall conductivity.展开更多
High quality single crystal CaFe4As3 was grown by using the Sn flux method. Unlike layered CaFe2As2, CaFe4As3 crystallizes in an orthorhombic three-dimensional structure. Two magnetic ordering transitions are observed...High quality single crystal CaFe4As3 was grown by using the Sn flux method. Unlike layered CaFe2As2, CaFe4As3 crystallizes in an orthorhombic three-dimensional structure. Two magnetic ordering transitions are observed at - 90 K and - 27 K, respectively. The high temperature transition is an antiferromagnetic（AF） ordering transition. However, the low temperature transition shows complex properties. It shows a ferromagnetic-like transition when a field is applied along b-axis, while antiferromagnetism-like transition when a field is applied perpendicular to b-axis. These results suggest that the low temperature transition at 27 K is a first-order transition from an AF state to a canted AF state. In addition, the low temperature electron specific heat coefficient reaches as high as 143 mJ/mol.K2, showing a heavy fermion behavior.展开更多
We have reported new magnetic and optical properties of Mn2O3 nanostructures. The nanostructures have been synthesized by the hydrothermal method combined with the adjustment of pH values in the reaction system. The p...We have reported new magnetic and optical properties of Mn2O3 nanostructures. The nanostructures have been synthesized by the hydrothermal method combined with the adjustment of pH values in the reaction system. The particular characteristics of the nanostructures have been analyzed by employing X-Ray diffraction （XRD）, scanning electron microscopy （SEM）, energy dispersive X-ray （EDX） analysis, transmission electron microscopy （TEM）, high resolution transmission electron microscopy （HRTEM）, Raman spectroscopy （RS）, UV-visible spectroscopy, and the vibrating sample magnetometer （VSM）. Structural investigation manifests that the synthesized Mn2O3 nanostructures are orthorhombic crystal. Magnetic investigation indicates that the Mn2O3 nanostructures are antiferromagnetic and the antiferromagnetic transition temperature is at TN = 83 K. Furthermore, the Mn2O3 nanostructures possess canted antiferromagnetic order below the Neel temperature due to spin frustration, resulting in hysteresis with large coercivity （1580 Oe） and remnant magnetization （1.52 emu/g）. The UV-visible spectrophotometry was used to determine the transmittance behaviour of Mn203 nanostructures. A direct optical band gap of 1.2 eV was acquired by using the Davis-Mott model. The UV-visible spectrum indicates that the absorption is prominent in the visible region, and transparency is more than 80% in the UV region.展开更多
Low-dose electron diffraction has been instrumental in determining the crystal structures of two compounds with metal-radical coordination frameworks{[Mn2^(Ⅱ)(NITIm)^(3)]CF^(3)SO_(3)·CH^(3)OH}n(1)and{[Mn_(2)^(Ⅱ...Low-dose electron diffraction has been instrumental in determining the crystal structures of two compounds with metal-radical coordination frameworks{[Mn2^(Ⅱ)(NITIm)^(3)]CF^(3)SO_(3)·CH^(3)OH}n(1)and{[Mn_(2)^(Ⅱ)(NITImMe_(2))_(3)]ClO_(4)}_(n)(2)that could never be grown to a crystal size large enough for single-crystal X-ray diffraction characterization.The compounds crystallize as nanocrystals upon addition of triflate(1)and perchlorate(2)anions and coordination of manganese(Ⅱ)with bis-chelate nitronyl nitroxide radicals NITImH(1)and NITImHMe_(2)(2)which are respectively 2-(2-imidazolyl)-and 2-(4,5-dimethylimidazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-3-oxide-1-oxyl.The two compounds have layered crystal structures in which cationic 2D metal-radical coordination polymers{[Mn2^(Ⅱ)(NITIm)_(3)]^(+)}_(n)(1)and{[Mn2^(Ⅱ)(NITImMe_(2))_(3)]^(+)}_(n)(2)are separated by layers of triflate(1)or perchlorate(2)anions.Magnetic measurements evidence a ferrimagnetic behavior within the 2D metal-radical sheets due to alternating antiferromagnetically coupled spins(S_(Mn)^(2+)=5/2 and S_(radical)=1/2).Both compounds exhibit a long-range 3D ordering of weak-ferromagnetic type due to spin canting with Curie temperatures T_(c)=45 K(1)and 40 K(2).This is associated with a field-induced metamagnetic transition from antiferromagnetic to ferromagnetic coupling of 2D metal-radical sheets.Studies of the crystal structures allows to rationalize how the molecular structure of nitronyl nitroxide radicals and of the counter-anions along with crystal packing affect the magnetic behavior related to interlayer distance and framework flexibility.These results are striking evidence that electron crystallography is a unique tool to solve structures of metal-organic compounds crystallizing as nanocrystals even with nitronyl nitroxide radical components too sensitive to typical electron doses.Overcoming the crystal size barrier,it allows the validation of chemical synthesis and the establishment of magneto-structural relationships fostering new advances in the design of molecule-based magnets.展开更多
Two isostructural 3D complexes[Mn(L)(N_(3))·MeOH]_(n)(1)and[Mn(L)(HCO_(2))·MeOH]n(2)(HL=pyrazine-2-carboxylic acid)were synthesized by using a solvothermal method.Magnetic studies indicate that 1 was a stron...Two isostructural 3D complexes[Mn(L)(N_(3))·MeOH]_(n)(1)and[Mn(L)(HCO_(2))·MeOH]n(2)(HL=pyrazine-2-carboxylic acid)were synthesized by using a solvothermal method.Magnetic studies indicate that 1 was a strong antiferromagnet,whereas 2 was a weak antiferromagnet with T_(N)38.5 K.展开更多
Analyses of the new slender-ship theory of wave resistance were made and corresponding calculation methods were proposed. Based on these theoretical methods, the calculations of wave resistance of near surface submers...Analyses of the new slender-ship theory of wave resistance were made and corresponding calculation methods were proposed. Based on these theoretical methods, the calculations of wave resistance of near surface submersible, Wigley hull and vertical/canted strut SWATHs were conducted. In the single and double integral parts of Green's function, the method of special function expansion and Chebyshev polynomial approach were adopted respectively. The formulas for zeroth-first-and second-order wave-making resistance were derived. In a towing tank, the calm water resistance experiment of SWATH model ASW-2 with canted strut was conducted and researched. The influences of waterline integral term, the surface mesh number, element node number, range of the integration and truncation of special function expansions on velocity potential and numerical results of resistance were investigated, and the difference between the zeroth-order and first-order wave resistance was analyzed. The theoretical calculation results agree well with the well-found model experimental results.展开更多
基金supported by the MOST(973 Program 2012CB821702)the NSFC(21171100,and 90922032)111 Project(B12015).
文摘Two new 3D pillared-layer cobalt(II)molecular magnetic materials,formulated as{[Co_(2)(TDA)(TZ)-(H_(2)O)_(2)]·H_(2)O}n(1)and{[Co_(3)(TDA)_(2)(bpy)_(3)]·6.75H_(2)O}_(n)(2)(H_(3)TDA=1H-1,2,3-triazole-4,5-dicarboxylic acid,HTZ=1H-1,2,4-triazole and bpy=4,4’-bipyridine),have been successfully assembled with H_(3)TDA and auxiliary ligands,respectively.
基金supported by the National Key R&D Program of China(Grant No.2022YFA1204002)Open Project Funding of the Key Laboratory of Intelligent Sensing System and Security(Ministry of Education)+3 种基金the International Science and Technology Cooperation Program under the 2023 Shanghai Action Plan for Science,Technology and Innovation(Grant No.23520711200)the National Natural Science Foundation of China(Grant Nos.52371246,12274323,52271188,12174287,and 12374118)the Natural Science Foundation of Shanghai(Grant No.23ZR1466800)Open Fund of the State Key Laboratory of Spintronics Devices and Technologies(Grant No.SPL-2412)。
文摘The anomalous Nernst effect(ANE),which enables energy conversion and harvesting in ferromagnetic materials through orthogonal charge generation relative to the heat gradient and magnetization,holds great promise for spintronic thermoelectric applications.However,achieving both perpendicular magnetic anisotropy(PMA)and an out-of-plane thermal gradient—two essential prerequisites for highly stable and efficient spintronic devices—contradicts the orthogonality condition required for ANE generation.In this study,we leverage the novel spincanting effect in ferrimagnetic CoTb films to realize a pronounced ANE response near the magnetic compensation temperature,yielding a remarkable ANE coefficient of 0.108μV/K.By further investigating the angular characteristics of the spin-canted state,we optimize and identify the ideal measurement scheme for spin-canting-mediated ANE.Our findings systematically elucidate the unique physical behavior of this unconventional ANE and demonstrate the potential of ferrimagnetic systems with strong PMA for developing high-performance thermoelectric devices.
文摘By using the derivative method, we obtained the same result with that of the previous work of Chen et al. in 2006. Different from the integral form, the derivative form of the surface expression published in this paper is derived from differential equation and based on the theory of non-imaging focusing heliostat proposed by Chen et al. in 2001. The comparison of the derivative form of fixed aberration correction surface has been made with that of integral form surface as well as that of spherical surface in concentrating the solar ray.
基金The project was supported by the National Natural Science Foundation of China(21461003)the Guangxi Natural Science Foundation of China(2016GXNSFFA380010 and 2016GXNSFAA380206)the Project of Guangxi Education Department(KY2016LX235)
文摘Based on the bent ligand 1 H-3-(3-pyridyl)-5-(4-pyridyl)-1,2,4-triazole(3,4?-Hbpt) with Co(Ⅱ) ions as well as a series of polycarboxylate co-ligands, three new coordination polymers were yielded, namely, {[Co(op)(3,4?-Hbpt)(H_2O)_3]?2 H_2O}n(1), [Co(cyc)(3,4′-Hbpt)(H_2O)]n(2) and [Co(pro)(3,4′-Hbpt)(H_2O)]n(3)(here, op = o-phthalic anion, cyc = 1,1-cyclobutanedicarboxylic anion, pro = propanedioic anion). In cooperation with the auxiliary polycarboxylate co-ligands, a variety of Co(Ⅱ) coordination networks, such as 1-D chain 1 and 2-D layer 2 and 3 have been assembled. The magnetic behaviors of compounds 1～3 were studied. All of them indicated the existence of interesting spin-canting behavior.
文摘A new three-dimensional nickel（Ⅱ） hydrogen-bonded molecular self assembly containing [（Ni（nicotinamide）2（thiocyanate）2（H2O）2] complex has been synthesized and characterized by single-crystal X-ray diffraction,FTIR spectroscopy,thermal analysis and magnetic measurements.Structural analysis reveals that the complex crystallizes in triclinic space group P1（crystal data a = 7.5574,b = 8.2683,c = 9.0056 A,α = 73.010,β = 69.698,γ = 66.51） and exhibits a distorted octahedral coordination sphere.Most interesting point in its structure is the involvement of sulphur atom of thiocyanate moiety in the trifurcated hydrogen bonding to build up the hydrogen-bonded self assembly.The magnetic behavior as determined by squid magnetometer（2~300 K temp.range） reveals dominating antiferromagnetic interaction followed by spin canting behavior below 20 K.
基金financially supported by the National Natural Science Foundation of China (Nos. 11674023, 51371015,51331002, and 51501004)Beijing Municipal Science and Technology Project (No. 217111000220000)
文摘It is the result of a systemic study about uniform hematite nanopallets with length of about 100 nm, width of about 30 nm, and thickness of less than 10 nm. The sample has superparamagnetic(SPM) properties above the blocking temperature of ～16 K. The temperature dependence of magnetization was well fitted by Bloch T^(3/2) law considering the dipolar interaction of the particles. The field dependence of magnetization was fitted with revised Langevin equation.The magnetization of the weak ferromagnetic(WF) canted spins contributes to the linear portion in the high field region;the surface uncompensated spins and the parasitic ferromagnetic moments due to the canted spins both contribute to the particle moments and the superparamagnetic behavior.
基金supported by the National Natural Science Foundation of China(Grant NO.12104407)the Natural Science Foundation of Zhejiang Province(Grant NO.LQ20A040004)
文摘The Heisenberg-Kitaev(HK)model on various lattices has attracted a lot of attention because it may lead to exotic states such as quantum spin liquid and topological orders.The rare-earth-based kagome lattice(KL)compounds Mg_(2)RE_(3)Sb_(3)O_(14)(RE=Gd,Er)and(RE=Nd)have q=0,120°order and canted ferromagnetic(CFM)order,respectively.Interestingly,the HK model on the KL has the same ground state long-range orders.In the theoretical phase diagram,the CFM phase resides in a continuous parameter region and there is no phase change across special parameter points,such as the Kitaev ferromagnetic(KFM)point,the ferromagnetic(FM)point and its dual FM point.However,a ground state property cannot distinguish a system with or without topological nontrivial excitations and related phase transitions.Here,we study the topological magnon excitations and related thermal Hall conductivity in the HK model on the KL with CFM order.The CFM phase can be divided into two regions related by the Klein duality,with the self dual KFM point as their boundary.We find that the scalar spin chirality,which is intrinsic in the CFM order,changes sign across the KFM point.This leads to the opposite Chem numbers of corresponding magnon bands in the two regions,and also the sign change of the magnon thermal Hall conductivity.
基金Project supported by the National Natural Science Foundation of China(Grant No.Y1JA011x11)
文摘High quality single crystal CaFe4As3 was grown by using the Sn flux method. Unlike layered CaFe2As2, CaFe4As3 crystallizes in an orthorhombic three-dimensional structure. Two magnetic ordering transitions are observed at - 90 K and - 27 K, respectively. The high temperature transition is an antiferromagnetic（AF） ordering transition. However, the low temperature transition shows complex properties. It shows a ferromagnetic-like transition when a field is applied along b-axis, while antiferromagnetism-like transition when a field is applied perpendicular to b-axis. These results suggest that the low temperature transition at 27 K is a first-order transition from an AF state to a canted AF state. In addition, the low temperature electron specific heat coefficient reaches as high as 143 mJ/mol.K2, showing a heavy fermion behavior.
基金Project supported by the Fundamental Development Fund and Chancellor Scholarship Program,China (Grant No.YJ2010-014)the Fundamental Research Funds for the Central Universities of China (Grant No. FRF-BR-09-007A)
文摘We have reported new magnetic and optical properties of Mn2O3 nanostructures. The nanostructures have been synthesized by the hydrothermal method combined with the adjustment of pH values in the reaction system. The particular characteristics of the nanostructures have been analyzed by employing X-Ray diffraction （XRD）, scanning electron microscopy （SEM）, energy dispersive X-ray （EDX） analysis, transmission electron microscopy （TEM）, high resolution transmission electron microscopy （HRTEM）, Raman spectroscopy （RS）, UV-visible spectroscopy, and the vibrating sample magnetometer （VSM）. Structural investigation manifests that the synthesized Mn2O3 nanostructures are orthorhombic crystal. Magnetic investigation indicates that the Mn2O3 nanostructures are antiferromagnetic and the antiferromagnetic transition temperature is at TN = 83 K. Furthermore, the Mn2O3 nanostructures possess canted antiferromagnetic order below the Neel temperature due to spin frustration, resulting in hysteresis with large coercivity （1580 Oe） and remnant magnetization （1.52 emu/g）. The UV-visible spectrophotometry was used to determine the transmittance behaviour of Mn203 nanostructures. A direct optical band gap of 1.2 eV was acquired by using the Davis-Mott model. The UV-visible spectrum indicates that the absorption is prominent in the visible region, and transparency is more than 80% in the UV region.
基金supported by CNRS collaborative research program(PRC 2017-2019 No.1536)the Russian Science Foundation(grant No.21-73-20079)+6 种基金Magdesign Project(ANR-22-CE29-0018-03)Platforms of the Grenoble Instruct-ERIC center(ISBG,UAR 3518 CNRS-CEA-UGA-EMBL)within the Grenoble Partnership for Structural Biology(PSB)supported by FRISBI(ANR-10-INBS-0005-02)GRAL,financed within the University Grenoble Alpes graduate school(Ecoles Universitaires de Recherche)CBH-EUR-GS(ANR-17-EURE-0003)The IBS-ISBG electron microscope facility is supported by the Région Auvergne-Rhône-Alpes,Fondation pour la Recherche Médicale(FRM),Fonds FEDER and the GIS-Infrastructures en Biologie Santéet Agronomie(IBiSA)supported by Grant-in-Aid for Scientific Research(No.25220803 and 22H02053)CResCent(Chirality Research Center)in Hiroshima University(the MEXT program for promoting the enhancement of research universities,Japan)Core-to-Core Program,A.Advanced Research Networks.
文摘Low-dose electron diffraction has been instrumental in determining the crystal structures of two compounds with metal-radical coordination frameworks{[Mn2^(Ⅱ)(NITIm)^(3)]CF^(3)SO_(3)·CH^(3)OH}n(1)and{[Mn_(2)^(Ⅱ)(NITImMe_(2))_(3)]ClO_(4)}_(n)(2)that could never be grown to a crystal size large enough for single-crystal X-ray diffraction characterization.The compounds crystallize as nanocrystals upon addition of triflate(1)and perchlorate(2)anions and coordination of manganese(Ⅱ)with bis-chelate nitronyl nitroxide radicals NITImH(1)and NITImHMe_(2)(2)which are respectively 2-(2-imidazolyl)-and 2-(4,5-dimethylimidazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-3-oxide-1-oxyl.The two compounds have layered crystal structures in which cationic 2D metal-radical coordination polymers{[Mn2^(Ⅱ)(NITIm)_(3)]^(+)}_(n)(1)and{[Mn2^(Ⅱ)(NITImMe_(2))_(3)]^(+)}_(n)(2)are separated by layers of triflate(1)or perchlorate(2)anions.Magnetic measurements evidence a ferrimagnetic behavior within the 2D metal-radical sheets due to alternating antiferromagnetically coupled spins(S_(Mn)^(2+)=5/2 and S_(radical)=1/2).Both compounds exhibit a long-range 3D ordering of weak-ferromagnetic type due to spin canting with Curie temperatures T_(c)=45 K(1)and 40 K(2).This is associated with a field-induced metamagnetic transition from antiferromagnetic to ferromagnetic coupling of 2D metal-radical sheets.Studies of the crystal structures allows to rationalize how the molecular structure of nitronyl nitroxide radicals and of the counter-anions along with crystal packing affect the magnetic behavior related to interlayer distance and framework flexibility.These results are striking evidence that electron crystallography is a unique tool to solve structures of metal-organic compounds crystallizing as nanocrystals even with nitronyl nitroxide radical components too sensitive to typical electron doses.Overcoming the crystal size barrier,it allows the validation of chemical synthesis and the establishment of magneto-structural relationships fostering new advances in the design of molecule-based magnets.
基金supported by the NSFC of China(21471112,21571139,21601134 and 11774178)the Natural Science Foundation of Tianjin(17JCQNJC05900)the Open Project Program of Key Laboratory of Preparation and Application of Environmentally Friendly Materials(Jilin Normal University),Ministry of Education,China(No.2017005).
文摘Two isostructural 3D complexes[Mn(L)(N_(3))·MeOH]_(n)(1)and[Mn(L)(HCO_(2))·MeOH]n(2)(HL=pyrazine-2-carboxylic acid)were synthesized by using a solvothermal method.Magnetic studies indicate that 1 was a strong antiferromagnet,whereas 2 was a weak antiferromagnet with T_(N)38.5 K.
文摘Analyses of the new slender-ship theory of wave resistance were made and corresponding calculation methods were proposed. Based on these theoretical methods, the calculations of wave resistance of near surface submersible, Wigley hull and vertical/canted strut SWATHs were conducted. In the single and double integral parts of Green's function, the method of special function expansion and Chebyshev polynomial approach were adopted respectively. The formulas for zeroth-first-and second-order wave-making resistance were derived. In a towing tank, the calm water resistance experiment of SWATH model ASW-2 with canted strut was conducted and researched. The influences of waterline integral term, the surface mesh number, element node number, range of the integration and truncation of special function expansions on velocity potential and numerical results of resistance were investigated, and the difference between the zeroth-order and first-order wave resistance was analyzed. The theoretical calculation results agree well with the well-found model experimental results.
