Fabrication of grouped magnetic heads

A new magnetic transducer has been developed for use in the measurement of mechanical displacement. Experiments suggest that the transducer could be used for various purposes: for instance, readout information from magnetic drums or disks of computers, nondestructive readout from thin-film memories, magnetic pattern recognition, and an unconventional flux sensor. The transducer is composed of flux-sensitive magnetic heads which are fabricated from a sheet of ferromagnetic thin film by photoetching process. By using the etching process, a large number of heads are produced simultaneously, and the heads are operated in a group. The characteristics, performances, and an application of grouped magnetic heads are described in this paper.     

Fabrication of magnetic nanodot arrays for patterned magnetic recording media

Fabrication processes of arrayed magnetic nanodots for the use of patterned magnetic recording media were reviewed. One candidate for the patterned media is ordered assemble of magnetic nanoparticles, and the other is patterned magnetic thin films fabricated using various micro/nano scale machining processes. For the formation of patterned masks and molds, lithography processes as well as self-organized pattern formation are utilized. For the deposition processes of magnetic dots, electrochemical deposition processes were widely used. These fabrication processes are reviewed mainly from recent reports. The recording systems for the patterned media including probe-type-recording are also overviewed.     

基于各向异性磁阻的开关芯片的制备及优化

采用射频磁控溅射法用Ta作为缓冲层,在集成电路晶元上制备NiFe薄膜,并研究分析了Ta缓冲层厚度以及Ta缓冲层溅射功率对NiFe磁阻薄膜性能的影响,通过测试结果可以得到,当溅射功率由小变大时,NiFe薄膜的磁阻值也由小变到大。当Ta层的厚度在5nm左右时,NiFe更容易形成(111)织构,这时其磁阻值也最大。利用优化后的工艺,在晶元上制备NiFe薄膜,测试结果显示出开关特性,其开关场分别在398和796A/m左右。     

Tunable metamaterial absorber based on resonant strontium titanate artificial atoms

Dynamic control of the absorption frequency and intensity of metamaterial absorbers has attracted considerable attention,and many kinds of tunable metamaterial absorbers have been proposed.Unfortunately,due to the integration of separate resonant unit and tunable unit,these designed metamaterial absorbers suffer from complex structure and low sensitivity.We numerically and experimentally demonstrate a tunable metamaterial absorber composed of artificial dielectric atoms as both resonant and tunable unit arrayed periodically in the background matrix on the metallic plate.Polarization insensitive and wide incident angle absorption band with simulated and experimental absorptivity of 99%and 96%at 9.65 GHz are achieved at room temperature.The absorption frequency can be gradually modulated by temperature,however,the absorption intensity at working frequency remains near unity.The dielectric atoms based tunable metamaterial absorbers with simple structure have potential applications as tempe rature sensors and frequency selective thermal emitters.     

Effect of impurity atoms in ferromagnets on magnetic relaxation

Results are presented from an experimental study of magnetic relaxation in iron specimens containing various amounts of carbon.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 47, No. 6, pp. 991–995, December, 1984.     

Fabrication of a magnetic helical mesostructured silica rod

We report a one-step synthesis of magnetic helical mesostructured silica (MHMS) by self-assembly of an achiral surfactant, magnetic nanocrystals with stearic acid ligands and silicate. This core-shell structured material consists of an Fe(3)O(4) superparamagnetic nanocrystal core and a highly ordered periodic helical mesoporous silica shell. We propose that the formation of the helical structure is induced by the interaction between the surfactant and dissociated stearic acid ligands. The MHMS obtained possesses superparamagnetism, uniform mesostructure, narrow pore size distribution, high surface area, and large pore volume. Furthermore, the drug release process is demonstrated using aspirin as a drug model and MHMS as a drug carrier in a sodium phosphate buffer solution.     

Plasmon-induced transparency by detuned magnetic atoms in trirod metamaterials

We demonstrate theoretically an analog of electromagnetically induced transparency (EIT) in the plasmonic metamaterial with the unit cell consisting of three parallel metallic rods. The electromagnetic mechanism for the EIT-like transmission is discussed based on our investigation of the localized surface plasmon resonances in three trirod configurations. We find that the transmission minima surrounding the transparency window on both sides correspond to two detuned magnetic resonances, which arise respectively from the antiphase plasmon couplings between a long rod and a short rod and between two short rods. A decrease of more than 10 times in the group velocity can be achieved for the trirod structure at the transparency window in the optical regime, and the EIT-like response can be well described by the theoretical model of two harmonic oscillators. This work not only reveals the EIT-like transmission in plasmonic metamaterial consisting of detuned magnetic "atoms," but also provides further insight into the plasmons' interactions, especially for metallic nanostructures comprising multiple metallic elements.     

Bio-inspired artificial cilia with magnetic dynamic properties

Inspired by the structure and properties of natural cilia, we focused on a facile template-free approach to prepare magnetic artificial cilia grown on the substrate (glass, PDMS, or others). In an applied magnetic field, the cilia formed spontaneously and immediately from magnetic nanoparticles and elastomeric polymer in a liquid solvent by bottom-up self-assembly. The length of prepared cilia could be in the scale of millimeter and reach a high aspect ratio of even over 100. We studied the effect of the magnetic strength applied and the size of nanoparticles to get tunable scale of cilia. The cilia show reversibly bending in an external magnetic field and this bending actuation gave some important functions: to transport macroscopic nonmagnetic materials on the cilia and to mix liquids.     

Fabrication of Al thin wire by utilizing controlled accumulation of atoms due to electromigration

A technique of fabricating metallic thin wires by utilizing effective collection of the atoms caused by electromigration, which is a phenomenon of atomic diffusion due to high current density, is presented. Atoms diffused by electron flow can be used for making metallic thin wires. To form metallic thin wire at the intended position, we used passivated Al thin film line that had a slit at the anode end of the line as a test sample. As a result of current applying, the Al thin wire of a high aspect ratio was fabricated.     

Fabrication of ultralow-profile micromachined inductor with magnetic core material

We have fabricated a microinductor with an ultralow profile by a microelectromechanical systems (MEMS) technique. The fabrication process uses UV-LIGA, dry etching, fine polishing, and electroplating to achieve high performance. The dimensions of the inductor are 1500 /spl mu/m/spl times/900 /spl mu/m/spl times/100 /spl mu/m. It has 41 turns, with coil width of 20 /spl mu/m, space of 20 /spl mu/m, and a high aspect ratio of 5 : 1. The inductance is 0.424 /spl mu/H and the quality factor (Q factor) is about 1.7 at a frequency of 1 MHz. The stray capacitance is approximately zero over the frequency range measured.     

Fabrication and characterization of thin films with perpendicular magnetic anisotropy for high-density magnetic recording

Perpendicular magnetic anisotropy (PMA) was first observed in thin films of cobalt-chromium alloys in 1974, and perpendicular magnetic recording was proposed in 1977. After less than ten years, a new technology for high-density magnetic recording is firmly established. This breakthrough of the science and technology of magnetic recording has been made possible mainly through the ingenuity and concerted efforts of researchers. The preparation, characterization, and application of the Co-Cr films featuring PMA have been extensively studied. This paper reviews the large number of reports on PMA films with emphasis on three areas: 1. processing of PMA films; 2. correlation of magnetic properties and microstructures of PMA films; and 3. state-of-art techniques for fabricating PMA films.Nomenclature PMA Perpendicular magnetic anisotropy - PMR Perpendicular magnetic recording - B Magnetic induction - H Magnetic field - H _c Coercivity - H _c, Perpendicular coercivity - H _d Demagnetizing field - H _k Anisotropy field - H Perpendicular anisotropy constant - M _r Remanent magnetization - M_s Saturation magnetization - P _Ar Argon pressure - T _s Substrate temperature - V _b Substrate bias voltage - Incidence angle - ₅₀ Half-width dispersion angle in the rocking curve - _c Curie temperature - ₀ Internal stress     

Fabrication and characterization of thin films with perpendicular magnetic anisotropy for high-density magnetic recording

Perpendicular magnetic anisotropy (PMA) was first observed in thin films of cobalt-chromium alloys in 1974, and perpendicular magnetic recording was proposed in 1977. After less than ten years, a new technology for high-density magnetic recording is firmly established. This breakthrough of the science and technology of magnetic recording has been made possible mainly through the ingenuity and concerted efforts of Iwasaki and other researchers. The preparation, characterization, and application of the Co-Cr films featuring PMA have been extensively studied. This paper reviews the large number of reports on PMA films with emphasis in three areas: (1) processing of PMA films; (2) correlation of magnetic properties and microstructures of PMA films; and (3) state-of-the-art techniques for fabricating PMA films.Nomenclature PMA Perpendicular magnetic anisotropy - PMR Perpendicular magnetic recording - B Magnetic induction - H Magnetic field - H _c Coercivity - H _c, Perpendicular coercivity - H _d Demagnetizing field - H _K Anisotropy field - H Perpendicular anisotropy constant - M _r Remanent magnetization - M _s Saturation magnetization - P _Ar Argon pressure - T _s Substrate temperature - V _b Substrate bias voltage - Incidence angle - ₅₀ Half-width dispersion angle in the rocking curve - _c Curie temperature - _o Internal stress     

不同结构镍纳米线阵列的制备及其磁性

采用直流电沉积在多孔有序氧化铝模板中制备了不同结构的有序镍纳米线阵列。采用SEM和TEM对所制备的镍纳米线的形貌和结构进行了表征。研究了镍纳米线不同结构对镍纳米线阵列磁性性能的影响规律．当电沉积电压为2．5V时制备的镍纳米线为多晶结构；电沉积电压4V时，镍纳米线为沿[220]择优取向的单晶结构；电沉积电压＞5V时，择优取向由[220]转为[111]方向．磁滞回线结果表明，单晶镍纳米线阵列与多晶纳米线阵列相比具有更高的矩形度，沿[111]择优取向的单晶纳米线相比沿[220]取向的单晶镍纳米线具有更大的矩形度，表现出显著的磁各向异性。     

Fabrication and characterization of FePt magnetic nanofibers via electrospinning technique

L1₀-structured platinum–iron (FePt) nanofibers were successfully synthesized by electrospinning technique, followed by calcination and reduction processes. In the preparation procedure, ferrous chloride tetrahydrate [Fe(Cl)₂?4H₂O] and iron nitrate nonahydrate [Fe(NO₃)₃?9H₂O] were, respectively, used as iron sources contained in precursor solution for electrospinning. Subsequently, the FePt nanofibers were obtained from the calcination in air and the followed reduction in hydrogen (H₂) of the as-spun FePt/PVP composite nanofibers. The FePt nanofibers were characterized by X-ray diffractometer, scanning electron microscopy, transmission electron microscopy, and superconducting quantum interference device magnetometry. It was found that the different iron salt used in the spinning solutions could highly affect the FePt nanofiber morphology, crystallite size, and the magnetic properties. The FePt nanofibers, resulted from the spinning solution containing iron dichloride tetrahydrate, were of better crystallinity and well-defined fibrous morphology with an average diameter of about 110 nm. Additionally, the considerably large coercivity of 10.27 kOe was recorded from the above FePt nanofibers.     

磁场凝固法制备过共晶MnBi/Bi磁性功能复合材料

Bi-Mn过共晶合金分别从3个不同状态凝固．合金中MnBi析出相均在磁场作用下以晶体的C轴平行磁场取向。形成规则排列组织，并且所得材料的剩磁都具有明显的各向异性。合金从低于355℃的固液两相区凝固时，铁磁性MnBi析出相在1．0T磁场中迅速形成均布的织构组织，并能在无磁场条件下保持稳定，材料无需热处理就有很好的剩磁性能。因此，磁场凝固技术能够高效率地、直接制备出性能优良的MnBi／Bi磁性功能复合材料。     

Fabrication of iron oxide nanoparticles: magnetic and electrochemical sensing property

In this paper, we report a simple synthesis of Fe₂O₃ nanoparticles using hydrothermal method. The formation of the sample was confirmed by X-ray diffraction analysis, X-ray photoelectron spectroscopy, Fourier transformed infrared spectroscopy, Raman spectroscopy and UV–Visible absorption spectroscopy. The average crystallite size of the synthesized Fe₂O₃ nanoparticles was estimated to be 61 nm and the particles were of good crystalline nature. Field emission-scanning electron microscopy study of the sample revealed that the Fe₂O₃ powder has rod-like morphology which is composed of nanoparticles. The vibrating sample magnetometer measurement shows that the nanoparticles possess ferromagnetic property. The synthesized Fe₂O₃ nanoparticles were used to modify glassy carbon electrode (Fe₂O₃/GCE) and the modified electrode was used to detect pyrocatechol (PC) in a pH 7.4 phosphate buffer solutions by cyclic voltammetry and chronoamperometry. At the Fe₂O₃/GCE, PC is oxidized at less positive potential with larger current response than the bare GCE. The proposed sensor exhibits great potential in the field of electrochemical sensing of PC.     

碳纳米管负载FeCoNi纳米复合材料的制备及磁性研究

采用湿化学法制备了碳纳米管负载组成可控的FexCo81-xNi19纳米复合材料,用XRD、TEM、SAED和EDX等技术进行表征,并用VSM测试样品的磁性能.结果表明,FexCo81-xNi19合金以颗粒状均匀分散在碳纳米管表面;当x=21、33、46时,FeCoNi合金均为体心立方和面心立方两相共存;其磁性能与合金的组成密切相关,随着合金中Fe含量的增加,矫顽力(Hc)下降,饱和磁化强度(Ms)显著增加;当x=46时,合金的磁性能最佳.     

Fe0.3Co0.7纳米有序阵列的制备和磁性

使用小孔径阳极氧化铝模板制备Fe0.3Co0.7纳米线有序阵列,研究了热处理对其磁性的影响.结果表明,热处理对Fe0.3Co0.7纳米线有序阵列的结晶度和局部形状各向异性有重大的影响,导致纳米阵列的矫顽力和剩磁比发生相应的变化.在适当热处理条件下获得的Fe0.3Co0.7纳米线有序阵列具有较高的矫顽力和剩磁比.在H2保护下550℃处理时获得最高的矫顽力2.63×105 A/m,矫顽力随着热处理时间的增加先是快速增加,然后趋向平缓,最后有一定程度的下降.