The optimal design method for an open Magnetic Resonance Imaging (MRI) superconducting magnet with an active shielding configuration is proposed. Firstly, three pairs of current rings are employed as seed coils. By ...The optimal design method for an open Magnetic Resonance Imaging (MRI) superconducting magnet with an active shielding configuration is proposed. Firstly, three pairs of current rings are employed as seed coils. By optimizing the homogeneity of Diameter Sphere Voltnne (DSV), the positions and currents of the seed coils will be obtained. Secondly, according to the positions and currents of the seed coils, the current density of superconducting wires is determined, and then the original sections for the coils can be achieved. An optimization for the homogeneity based on the constrained nonlincar optimization method is employed to determine the coils with good homogeneity. Thirdly, the magnetic field generated by previous coils is set as the background field, then add two coils with reverse current, and optimize the stray field line of 5 Gauss in a certain scope. Finally, a further optimization for the homogeneity is used to get Final coils. This method can also be used in the design of other axisynmaetfic superconducting MRI magnets.展开更多
Antiferromagnetic (AFM) materials have attracted wide attention in spin-orbit torque (SOT)-based spintronic due to its abundant spin-dependent properties and unique advantage of immunity against external field perturb...Antiferromagnetic (AFM) materials have attracted wide attention in spin-orbit torque (SOT)-based spintronic due to its abundant spin-dependent properties and unique advantage of immunity against external field perturbations.To act as the charge-to-spin conversion source in energy-saving spintronic devices,it is of great importance for the AFM material to possess a large spin torque efficiency(ξDL).In this work,using the spin torque ferromagnetic resonance (ST-FMR) technique and a Mn2Au/Ni Fe(Py) bilayer system,we systemically study the ξDLof AFM Mn2Au films with different crystal structures.Compared with polycrystalline Mn2Au with effective ξDL<0.051,we show a much larger ξDLof~0.333 in single-crystal Mn2Au,which arises from the large spin Hall conductivity instead of electrical resistivity.Moreover,with a further contribution of interfacial effects,the effective ξDLof single-crystalline Mn2Au/Py system increases to 0.731,which is more than two times larger than the value of ~0.22 reported for the Mn2Au/CoFeB system.By utilizing the largeξDLof Mn2Au in a perpendicularly magnetized Mn Ga/Mn2Au system,energy-efficient deterministic magnetization switching with a current density at ~10^(6)A cm^(-2)is achieved.Our results reveal a significant potential of Mn2Au as an efficient SOT source and shed light on its application in future AFM material-based SOT integration technology.展开更多
Magnetic nanoparticles have emerged as a powerful tool for magnetic resonance imaging, biodetection, drug delivery, and hyperthermia. This review focuses on the biological detection of magnetic nanoparticles as well a...Magnetic nanoparticles have emerged as a powerful tool for magnetic resonance imaging, biodetection, drug delivery, and hyperthermia. This review focuses on the biological detection of magnetic nanoparticles as well as their physicochemical properties. Substantial progress in the sensitivity of detection has been made by developing variety of methods. Five applications of magnetic nanoparticles in biological detection are discussed in this review: magnetic separation, magnetic sensing, magnetic manipulation, magnetic catalysis, and signal enhancer for surface plasmon resonance(SPR). Finally, some future trends and perspectives in these research areas are outlined.展开更多
基金supported by the National Natural Science Foundation of China(No.50577063)
文摘The optimal design method for an open Magnetic Resonance Imaging (MRI) superconducting magnet with an active shielding configuration is proposed. Firstly, three pairs of current rings are employed as seed coils. By optimizing the homogeneity of Diameter Sphere Voltnne (DSV), the positions and currents of the seed coils will be obtained. Secondly, according to the positions and currents of the seed coils, the current density of superconducting wires is determined, and then the original sections for the coils can be achieved. An optimization for the homogeneity based on the constrained nonlincar optimization method is employed to determine the coils with good homogeneity. Thirdly, the magnetic field generated by previous coils is set as the background field, then add two coils with reverse current, and optimize the stray field line of 5 Gauss in a certain scope. Finally, a further optimization for the homogeneity is used to get Final coils. This method can also be used in the design of other axisynmaetfic superconducting MRI magnets.
基金supported by the Agency for Science,Technology and Research (A*STAR) of Singapore (A1983c0036)the Singapore Ministry of Education (MOE2018-T2-2043)A*STAR IAF-ICP 11801E0036。
文摘Antiferromagnetic (AFM) materials have attracted wide attention in spin-orbit torque (SOT)-based spintronic due to its abundant spin-dependent properties and unique advantage of immunity against external field perturbations.To act as the charge-to-spin conversion source in energy-saving spintronic devices,it is of great importance for the AFM material to possess a large spin torque efficiency(ξDL).In this work,using the spin torque ferromagnetic resonance (ST-FMR) technique and a Mn2Au/Ni Fe(Py) bilayer system,we systemically study the ξDLof AFM Mn2Au films with different crystal structures.Compared with polycrystalline Mn2Au with effective ξDL<0.051,we show a much larger ξDLof~0.333 in single-crystal Mn2Au,which arises from the large spin Hall conductivity instead of electrical resistivity.Moreover,with a further contribution of interfacial effects,the effective ξDLof single-crystalline Mn2Au/Py system increases to 0.731,which is more than two times larger than the value of ~0.22 reported for the Mn2Au/CoFeB system.By utilizing the largeξDLof Mn2Au in a perpendicularly magnetized Mn Ga/Mn2Au system,energy-efficient deterministic magnetization switching with a current density at ~10^(6)A cm^(-2)is achieved.Our results reveal a significant potential of Mn2Au as an efficient SOT source and shed light on its application in future AFM material-based SOT integration technology.
基金supported by the National Natural Science Foundation of China(2014M561073,51173139)the Program for Young Outstanding Scientists of Institute of Chemistry,and the Chinese Academy of Science(Y41Z011)
文摘Magnetic nanoparticles have emerged as a powerful tool for magnetic resonance imaging, biodetection, drug delivery, and hyperthermia. This review focuses on the biological detection of magnetic nanoparticles as well as their physicochemical properties. Substantial progress in the sensitivity of detection has been made by developing variety of methods. Five applications of magnetic nanoparticles in biological detection are discussed in this review: magnetic separation, magnetic sensing, magnetic manipulation, magnetic catalysis, and signal enhancer for surface plasmon resonance(SPR). Finally, some future trends and perspectives in these research areas are outlined.