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The study of the shape anisotropy in patterned permalloy films

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Chinese Physics B 2007年第6期16卷 1725-1727页

作者：张栋翟亚翟宏如 School of Physics Science and Information Engineering Liaocheng University Liaocheng 252059 China Department of Physics Southeast University Nanjing 210096 China National Laboratory of Solid Microstructure Center for Materials Analysis Nanjing University Nanjing 210093 China

In this paper a systematic ferromagnetic resonance study shows that an in-plane magnetic anisotropy in the patterned micron octagon permalloy （Ni80Fe20） elements is mainly determined by the element geometry. The easy-axis is along the edge of the elements, and the hard-axis is along the diagonal. The shape anisotropy of the octagon elements is determined by square and equilateral octagon, and the theoretical calculation was studied on the shape anisotropy. The shape anisotropy of rectangular was calculated by using the same theory.

关键词： patterned film shape anisotropy ferromagnetic resonance

Microwave Application shape anisotropy of Micro-sized Bamboo Blind shape

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Journal of Iron and Steel Research International 2012年第S2期19卷 826-829页

作者： Keisuke Fujisaki Toyota Technological Institute

Electromagnetic anisotropic characteristics in micro-sized water bamboo blind shape are observed by high frequency electromagnetic computation,which is applied to the material constants *** assuming that the micro-sized unit structure is repeated in 3-dimensional space and its size is much smaller than the electromagnetic wave length,the micro-sized electromagnetic field calculation is carried *** the micro-structure shapes of the material are different even if they are the same volume rate,different dielectric constant characteristics are *** reasons are considered to be a generation of de-electrification within the dielectric material.

关键词： micro-sized model shape anisotropy microwave bamboo blind shape

Magnetically Induced Anisotropic Interaction in Colloidal Assembly

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Precision Chemistry 2023年第5期1卷 272-298页

作者： Qingsong Fan Zhiwei Li Chaolumen Wu Yadong Yin Department of Chemistry University of CaliforniaRiversideCalifornia 92521United States

The wide accessibility to nanostructures with high uniformity and controllable sizes and morphologies provides great opportunities for creating complex superstructures with unique *** anisotropic nanostructures as the building blocks significantly enriches the superstructural phases,while their orientational control for obtaining long-range orders has remained a significant *** solution is to introduce magnetic components into the anisotropic nanostructures to enable precise control of their orientations and positions in the superstructures by manipulating magnetic *** the importance of magnetic anisotropy in colloidal assembly,we provide here an overview of magnetic field-guided self-assembly of magnetic nanoparticles with typical anisotropic shapes,including rods,cubes,plates,and *** Review starts with discussing the magnetic energy of nanoparticles,appreciating the vital roles of magneto-crystalline and shape anisotropies in determining the easy magnetization direction of the anisotropic *** then introduces superstructures assembled from various magnetic building blocks and summarizes their unique properties and intriguing *** concludes with a discussion of remaining challenges and an outlook of future research opportunities that the magnetic assembly strategy may offer for colloidal assembly.

关键词： colloidal self-assembly magnetic field-guided self-assembly magnetic nanoparticles magnetic anisotropy superstructures magneto-crystalline anisotropy shape anisotropy

shape anisotropic Fe3O4 nanotubes for efficient microwave absorption

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Nano Research 2020年第3期13卷 621-629页

作者： Jialiang Pan Honggui Guo Min Wang Hui Yang Haowen Hu Peng Liu Hongwei Zhu State Key Lab of New Ceramics and Fine Processing School of Materials Science and EngineeringTsinghua UniversityBeijing100084China The First Scientific Research Institute of Wuxi Wuxi214035China

Although Fe3O4 particles have exhibited excellent microwave absorbing capacity and widely used in practical application due to the synergistic effect of magnetic loss and dielectric loss,their applications are still limited for the required high mass fraction in *** overcome this problem,the development of Fe3O4 materials with low dimensional structures is *** this study,the shape anisotropic Fe3O4 nanotubes(NTs)with low mass ratios were applied to realize efficient microwave *** NTs with different aspect ratios were prepared through facile electrospinning followed by two-step thermal treatments and mechanical *** cross-linked nanotubular structure enabled the absorbers to have much higher electrical conductivity,multiple scattering,polarization relaxation and better anti-reflection surface,while the shape anisotropic NTs maintained significant multiple resonances with stronger *** all were beneficial to microwave absorption with enhanced dielectric loss,magnetic loss and sterling impedance *** showed that the absorber with 33.3 wt.%of short Fe3O4 NTs had minimum reflection loss of-58.36 dB at 17.32 GHz with a thickness of 1.27 mm,and had the maximum effective absorbing bandwidth(EAB)of 5.27 GHz when the thickness was 1.53 *** absorber with 14.3 wt.%of long Fe3O4 NTs presented the widest EAB in certain radar band with attenuated 80.75%X band and 85%Ku band energy bellow-10 dB at the thickness of 2.65 and 1.53 mm,*** study provided an approach for the development of shape anisotropic magnetic absorbing materials,and broadened their practical applications as magnetic absorbers.

关键词： Fe3O4 nanotubes shape anisotropy multiple resonances microwave absorption

Demagnetizing factors in patterned CoNiFe films with rectangular elements

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Chinese Physics B 2013年第5期22卷 421-424页

作者：章羽张栋王昱坤尹玉莉黄兆聪罗琛翟亚 Department of Physics Southeast University School of Physics Science and Information Engineering Liaocheng University

CoNiFe patterned films with rectangular elements, all 600-nm wide but of different lengths, were fabricated and inves- tigated by ferromagnetic resonance experiment and micromagnetic simulation. An in-plane magnetic uniaxial anisotropy was exhibited, and its value increases with the increase of the aspect ratio of the elements, which was fitted by the model, including a quasi-ellipsoid demagnetizing field and a non-uniform demagnetizing field. The relative importance of the non- uniform demagnetizing field decreased from 0.26 to 0.16 with the increase of the length-width aspect ratio of the patterned element from 1.5 to 10. The demagnetizing factors in the three principal axes were determined from the experimental data of ferromagnetic resonance, which agreed reasonably well with the values calculated by micromagnetic simulation. The calculation also indicated that the interaction between elements could be neglected when the edge-to-edge spacing between neighboring elements was larger than 3 μm in our patterned films.

关键词： patterned film shape anisotropy ferromagnetic resonance

Fabrication and magnetic properties of Ni_(0.5)Zn_(0.5)Fe_2O_4 nanofibres by electrospinning

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Chinese Physics B 2009年第11期18卷 4960-4965页

作者：向军沈湘黔宋福展刘明权 School of Materials Science and Engineering Jiangsu University

NiZn ferrite/polyvinylpyrrolidone composite fibres were prepared by sol,el assisted electrospinning. Ni0.5Zn0.5Fe2O4 nanofibres with a pure cubic spinel structure were obtained subsequently by calcination of the composite fibres at high temperatures. This paper investigates the thermal decomposition process, structures and morphologies of the electrospun composite fibres and the calcined Ni0.5Zn0.5Fe2O4 nanofibres at different temperatures by thermo-gravimetric and differential thermal analysis, x-ray diffraction, Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The magnetic behaviour of the resultant nanofibres was studied by a vibrating sample magnetometer. It is found that the grain sizes of the nanofibres increase significantly and the nanofibre morphology graduMly transforms from a porous structure to a necklace-like nanostructure with the increase of calcination tempera-ture. The Ni0.5Zn0.5Fe2O4 nanofibres obtained at 1000℃ for 2h are characterized by a necklace-like morphology and diameters of 100-200nm. The saturation magnetization of the random Ni0.5Zn0.5Fe2O4 nanofibres increases from 46.5 to 90.2 emu/g when the calcination temperature increases from 450 to 1000℃. The coercivity reaches a maximum value of 11.0 kA/m at a calcination temperature of 600℃. Due to the shape anisotropy, the aligned Ni0.5Zn0.5Fe2O4 nanofibres exhibit an obvious magnetic anisotropy and the ease magnetizing direction is parallel to the nanofibre axis.

关键词： NiZn ferrite nanofibre electrospinning magnetic property shape anisotropy

Micromagnetic simulation on magnetic properties of Nd2Fe14B/α-Fe nanocomposites with Fe nanowires as the soft phase

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Frontiers of Materials Science 2018年第4期12卷 348-353页

作者： Wei LI Lizhong ZHAO Zhongwu LIU School of Materials Science and Engineering South China University of TechnologyGuangzhou 510640China

Fe nanowire array with strong shape anisotropy was employed as the soft phase in Nd-Fe-B based nanocomposites. The effects of the Fe nanowire distribution on magnetic properties of the nanocomposites were investigated by micromagnetic simulation. The results indicate that the shape anisotropy of Fe wires added in the same direction as the uniaxial magnetocrystalline anisotropy of the hard phase cannot increase the coercivity of the nanocomposite. When the nanowires are distributed perpendicular to the easy axis of the hard phase, the shape anisotropy of soft phase can retard the moments from rotating to the full reversed direction, leading to enhanced coercivity. In addition, with increasing the nanowire diameter, the coercivity of the nanocomposite decreases, but the dipolar interaction shows different roles in magnetic reversal of nanocomposite for different distributions of nanowires. The current results suggest that the coercivity of the Nd2Fe14B/α-Fe nanocomposite can be enhanced by introducing the soft magnetic nanowire array with the diameter less than the exchange length and with the long axis along the direction other than the easy axis of hard phase.

关键词： Nd 2 Fe 14 B/α-Fe nanocomposite micromagnetic simulation Fe nanowires shape anisotropy exchange coupling

Controllable preparation and microwave absorption properties of shape anisotropic Fe_(3)O_(4) nanobelts

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Journal of Materiomics 2021年第5期7卷 957-966页

作者： Jialiang Pan Rujing Zhang Jun Ling Min Wang Zechen Li Zhen Zhen Limin He Hongwei Zhu State Key Lab of New Ceramics and Fine Processing School of Materials Science and EngineeringTsinghua UniversityBeijing100084China The First Scientific Research Institute of Wuxi Wuxi214035JiangsuChina Key Laboratory of Science and Technology on Advanced Corrosion and Protection for Aviation Material AECC Beijing Institute of Aeronautical MaterialsBeijing100095China

To substantially prevent electromagnetic threatens,microwave absorbing materials(MAMs)are required to eliminate surplus electromagnetic *** a typical MAM,Fe_(3)O_(4) particles with complex permittivity and permeability have been widely applied due to the coexistence of magnetic loss and dielectric ***,the necessary high mass fraction significantly limited its applications,thus Fe_(3)O_(4) nanostructures have been extensively investigated to overcome this *** this work,uniform Fe_(3)O_(4) nanobelts were prepared by electrospinning and two-step thermal *** controlling the composition and viscosity of the electrospinning precursor solution,Fe_(3)O_(4) nanobelts with tunable lateral sizes(200 nme1 mm)were *** samples with low content(only 16.7 wt%)Fe_(3)O_(4) exhibited wide maximum effective absorbing bandwidths(EAB)over 3 GHz,and Fe_(3)O_(4) nanobelts with smaller lateral sizes showed a maximum EAB of 4.93 ***,Fe_(3)O_(4) nanobelts with smaller lateral sizes presented superior reflection loss properties,the lowest reflection loss reached-53.93 dB at 10.10 GHz,while the maximum EAB was up to 2.98 *** excellent microwave reflection loss of Fe_(3)O_(4) nanobelts was contributed to the enhanced synergistic effect of magnetic loss,dielectric loss,and impedance matching,originated from the hierarchically cross-linked networks and shape *** study could broaden the practical applications of magnetic absorbers,and provided an approach for the development of shape anisotropic magnetic materials.

关键词： Fe_(3)O_(4) Nanobelts shape anisotropy Microwave absorption Reflection loss

Self-Assembled Plasmonic Pyramids from Anisotropic Nanoparticles for High-Efficient SERS

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Journal of Analysis and Testing 2017年第4期1卷 335-343页

作者： Wenjuan Yang Kae Jye Si Pengzhen Guo Dashen Dong Debabrata Sikdar Malin Premaratne Wenlong Cheng Department of Chemical Engineering Faculty of EngineeringMonash UniversityClaytonVIC 3800Australia The Melbourne Centre for Nanofabrication 151 Wellington RoadClaytonVIC 3168Australia Advanced Computing and Simulation Laboratory(AvL) Department of Electrical and Computer Systems EngineeringFaculty of EngineeringMonash UniversityClaytonVIC 3800Australia Department of Chemistry Faculty of Natural SciencesImperial College LondonExhibition RoadSouth KensingtonLondon SW72AZUK

Surface-enhanced Raman scattering(SERS)substrates play important roles for the enhancement of inelastic scattering *** substrates such as roughened electrodes and colloidal aggregates suffer from well-known signal reproducibility issues,whereas for current dominant two-dimensional planar systems,the hot spot distributions are limited by the zero-,one-or two-dimensional *** introduction of a three-dimensional(3D)system such as a pyramid geometry breaks the limitation of a single Cartesian SERS-active area and extends it into the z-direction,with the tip potentially offering additional benefits of strong field enhancement and high ***,current 3D pyramidal designs are restricted to film deposition on prepared pyramid templates or self-assembly in pyramidal molds with spherical building blocks,hence limiting their SERS ***,we report on the fabrication of a new class of low cost and well-defined plasmonic nanoparticle pyramid arrays from different anisotropic shaped nanoparticles using combined top-down lithography and bottom-up self-assembly *** pyramids exhibit novel optical scattering properties that can be exploited for the design of reproducible and sensitive SERS *** SERS intensity was found to decrease drastically in accordance with a power law function as the focal planes move from the apex of the pyramid structure towards the *** comparison to sphere-based building blocks,pyramids assembled from anisotropic rhombic dodecahedral gold nanocrystals with numerous sharp tips exhibited the strongest SERS *** Abstract Macroscale pyramidal array films with plasmonic tunability as a new class of SERS substrate for sensitive detection of chemicals.

关键词： Self-assembly Pyramid Plasmonics shape anisotropy Surface-enhanced Raman scattering