Magnetic property and microstructure of SmCo magnetic recording films

Cr/SmCo/Cr thin films with Sm concentration of 37.7 at.% were deposited on glass substrates by magnetron sputtering. Measurement of magnetic properties showed that the SmCo film possessed good magnetic anisotropy, a high coercivity of 3019 kA/m and low magnetic exchange coupling. Microstructure analysis showed that crystallized SmCo5 magnetic phase, non-magnetic SmCo2 phase and Sm2Co7 phase co-existed in the film. The non-magnetic SmCo2 phase might function as isolator of SmCo grains, leading to a decrease of magnetic exchange coupling. Moreover, a Cr2O3 oxide layer which could protect the SmCo layer from oxidation formed at the surface of the Cr cap layer.

TeO_(x) Thin Films for Write-Once Optical Recording Media

TeO_x thin films were prepared by vacuum evaporation of TeO_2 powder. Structural characteristic and surface mor-phology of the as-deposited films was analyzed by using X-ray photoelectron spectroscopy, transmission electron microscopy, X-ray diffractometer and atomic force microscopy. It was found that the films represented a two component system comprising Te particies dispersed in an amorphous TeO2 matrix. The dispersed Te particies were in a crystalline state. The TeOx films showed a finely granular structure and a rough surface. Results of the statie recording test showed that the TeO_x films had good writing sensitivity for short-wavelength laser beam (514.5 nm). Primary results of the dynamic test at 514.5 nm were also reported. The TeO_x films were suitable for using as a blue-green wavelength high density optical storage medium.

Study on Physical Process of Surface Oxidation of Rare Earth-Transition Metal Amorphous Magneto-Optical Thin Films

By using surface effects(Auger electron spectroscopy,X-ray photoelectron spectroscopy,polar Kerr effect)and volume effects(magnetization,torque curve)the physical process of surface oxidation of rare earth-transition metal amorphous magneto-optical thin films was studied in this paper.The rare earth elements oxidize preferentially and rich at the film surface,and the transition metals deplete in oxidation layer.Fe_2O_3 in the surface oxidation layer contributes to the planar magnetization,and thereby the anomalous peak appears near 180° on the torque curves and the amplitude of the peaks is related to the depth of surface oxidation layers.The iron bonds to oxygen easier than the cobolt.RE-Co magneto-optieal thin films have good properties of resistance to oxidation and humidity.

Magneto-Optical Properties of Wider Gap Semiconductors ZnMnTe and ZnMnSe Films Prepared by MBE

TheⅡ-Ⅵbased magnetic semiconductors with a direct and wide optical bandgap are expected to show high potential for optical applications utilizing short wavelength laser diodes(LDs),such as 532-nm green and475-nm blue LDs.We have confirmed that the Faraday rotationθ_F in the ZnMnTe and ZnMnSe films deposited on quartz glass(QG)and sapphire(SA)substrates by using molecular beam epitaxy(MBE)is large near the absorption edge.This paper reports the magneto-optical properties of ZnMnTe and ZnMnSe films synthesized on the QG and SA substrates,and shows the result of a direct Faraday rotation observation successfully made for the ZnMnTe films under 1.28-kHz alternating magnetic fields.The optical absorption characteristics of the ZnMnTe films grown on the SA substrates by MBE are discussed by comparing them with the optical absorption properties and photoluminescence spectra of theⅡ-ⅥZnTe parent single crystals.

Template-assisted growth of Co-BaTiO_(3) vertically aligned nanocomposite thin films with strong magneto-optical coupling effect

Oxide-metal based nanocomposite thin films have attracted great interests owing to their unique anisotropic structure and physical properties.A wide range of Au-based oxide-metal nanocomposites have been demonstrated,while other metal systems are scarce due to the challenges in the initial nucleation and growth as well as possible interdiffusions of the metallic nanopillars.In this work,a unique anodic aluminum oxide(AAO)template was used to grow a thin Co seed layer and the following self-assembled metal-oxide(Co-BaTiO_(3))vertically aligned nanocomposite thin film layer.The AAO template allows the uniform growth of Co-seeds and successfully deposition of highly ordered Co pillars(with diameter<5 nm and interval between pillars<10 nm)inside the oxide matrix.Significant magnetic anisotropy and strong magneto-optical coupling properties have been observed.A thin Au-BaTiO_(3) template was also later introduced for further enhanced nucleation and ordered growth of the Co-nanopillars.Taking the advantage of such a unique nanostructure,a large out-of-plane(OP)coercive field(Hc)of~5000 Oe has been achieved,making the nanocomposite an ideal candidate for high density perpendicular magnetic tunneling junction(p-MTJ).A strong polar magneto-optical Kerr effect(MOKE)has also been observed which inspires a novel optical-based reading method of the MTJ states.

Improvement on the magneto-optical Kerr effect of cobalt film with a quadrilayer structure

The magneto-optical Kerr effect of the HfO2/Co/HfO2/A1 multilayer structure is investigated in this work, and an ob- vious cavity enhancement of the Kerr response for the HfO2 semiconductor is found both theoretically and experimentally. Surprisingly, a maximum value of about -3 of the polar Kerr rotation for s-polarized incident light is observed in our experiment. We propose that this improvement on the Kerr effect can be attributed to the multiple reflection and optical interference in the cavity, which can also be proved by simulation using the finite element method.

Influence of Ti on Microstructure and Magnetic Properties of FePt Granular Films

在室温下,应用对靶直流磁控溅射设备在普通玻璃基片上制备了FePt(30 nm)／Ti(t nm)颗粒膜样品,随后,在真空中进行了原位退火。详细研究了Ti衬底层对FePt颗粒膜的微结构和磁特性的影响。X射线衍射图谱表明样品形成了较有序的L10织构,Ti和FePt形成了三元FePtTi合金。当Ti层厚度t=5 nm、退火温度Ta=500℃时,样品具有高度有序的L10织构、小的颗粒尺寸和优异的磁特性。矫顽力超过了6．7 kOe,饱和磁化强度为620emu／cc。并且具有较小的开关场分布。结果表明FePt／Ti颗粒膜系统可作为超高密度磁记录介质的候选者。

A flexible,thin-film microchannel electrode array device for selective subdiaphragmatic vagus nerve recording

The vagus nerve(VN)plays an important role in regulating physiological conditions in the gastrointestinal(GI)tract by communicating via the parasympathetic pathway to the enteric nervous system(ENS).However,the lack of knowledge in the neurophysiology of the VN and GI tract limits the development of advanced treatments for autonomic dysfunctions related to the VN.To better understand the complicated underlying mechanisms of the VN-GI tract neurophysiology,it is necessary to use an advanced device enabled by microfabrication technologies.Among several candidates including intraneural probe array and extraneural cuff electrodes,microchannel electrode array devices can be used to interface with smaller numbers of nerve fibers by securing them in the separate channel structures.Previous microchannel electrode array devices to interface teased nerve structures are relatively bulky with thickness around 200µm.The thick design can potentially harm the delicate tissue structures,including the nerve itself.In this paper,we present a flexible thin film based microchannel electrode array device(thickness:11.5µm)that can interface with one of the subdiaphragmatic nerve branches of the VN in a rat.We demonstrated recording evoked compound action potentials(ECAP)from a transected nerve ending that has multiple nerve fibers.Moreover,our analysis confirmed that the signals are from C-fibers that are critical in regulating autonomic neurophysiology in the GI tract.

Effects of Ag layers on the microstructure and magnetic properties of CoPt/BN multilayer films

Ag/[BN/CoPt]5/Ag and [BN/Ag/CoPt]5/Ag thin films were deposited on glass substrates by magnetron sputtering and then annealed in vac- uum at 600 ℃ for 30 min. The structures and magnetic properties of CoPt/BN multilayer films were investigated as a function of Ag layer thickness. It was found that the face-centered tetragonal （fct） （001） texture of CoPt was improved greatly by introducing the Ag toplayer or sublayer together with an Ag underlayer. Good （001）-oriented growth, low intergrain interactions as well as high perpendicular anisotropy can be obtained in the Ag（3 nm）/[BN（2.5 nm）/CoPt（3 nm）]5/Ag（7 nm） and [BN（2.5 nm）/Ag（2 nm）/CoPt（3 nm）]5/Ag（10 nm） films, which become potential candidates for ultrahigh density magnetic recording media.

Microstructure and magnetic properties of Ti/Co/Ti films

The two series of as-deposited and annealed Ti/Co/Ti thin films were deposited by magnetron sputtering onto glass substrates at room temperature. The structural and magnetic properties of the films at room temperature were investigated as function of Co layer thickness. X-ray diffraction (XRD) profiles show Co nanograins are formed as the hexagonal-close-packed (hcp) structure. The perpendicular coercivity of the Ti(15 nm)/Co(30 nm)/Ti(15 nm) film annealed at 450 ℃ for 30 min is about 288 kA·m-1.

Effects of Nd Doping on Magnetic-Optical Properties of GdFeCo Thin Films

The GdFeCo and NdGdFeCo thin films were prepared by sputtering, and their hysteresis loops, the temperature dependence of the saturation magnetization Ms and the magneto-optical Kerr spectrum in the visible light range were measured. By studying the effects of light rare earth element Nd doping on the magneto-optical Kerr rotation angle of GdFeCo thin films, it is found that proper Nd additives in GdFeCo films could enhance Kerr rotation at short wavelengths. So it could be better medium used as the readout layer of center aperture detection magnetically induced super resolution （CAD-MSR）.

Ll_0 FePt thin films with 001crystalline growth fabricated by ZnO addition and rapid thermal annealing

FePt films with a high degree of order S of the L10 structure （S 〉 0.90） and well defined [001] crystalline growth perpendicular to the film plane are fabricated on thermally oxidized Si substrates by the addition of ZnO and a successive rapid thermal annealing （RTA） process. The optimum condition to prepare high-ordering L10 FePtZnO films is 20 vol% ZnO addition and 450 ℃ annealing. The effect of the ZnO additive on the ordering process of the L10 FePtZnO films is discussed. In the annealing process, Zn atoms move to the film surface and evaporate. The motion of the Zn atoms accelerates the intergrain exchange and decreases the ordering temperature.

Preparation and Characterization of Rare Earth Metal and Alloy Target Materials for Manufacturing Magneto-Optical Disks

The studies were made on the preparation processes of the rare earth metal and alloy target materials and their characterization. In this work the rare earth metals were prepared by electrolysis of the oxide in molten salt for Nd metal and metallothermic reduction of the fluorides for Gd, Tb, Dy metals. After vacuum refining and distillation purification these rare earth metals were used for manufacturing the element targets, mosaic targets and as the starting materials of preparing the rare earth-transition metal (RE-TM) alloy targets. The four kinds of Dy-FeCo, NdDy-FeCo, Tb-FeCo and GdTb-FeCo alloy targets with diameter of 100 mm and thickness of 3 mm were prepared using powder metallurgical technique. The oxygen content and microstructure of the prepared RE-TM cast alloys and sintered targets were analyzed. The features and requirements of the RE-TM alloy sputtering target materials were also discussed.

Thickness Dependence of Magnetic Properties in DyFeCo Films

Films of amorphous DyFeCo were deposited on glass substrates using RF sputtering deposition system. The thickness dependence of the coercivity of DyFeCo films prepared under the same sputtering conditions was investigated. It is found that the composition is nearly thickness independent, while the coercivity is shown to increase with the film thickness increasing at the beginning, then above a certain thickness decrease with the thickness increasing. The thickness dependence of the coercivity is believed to be due to microstructure-induced variations in the short-range order during the film growth. Key words magneto-optical films - coercivity - microstructure CLC number O 469 Foundation item: Supported by the Natural Science Foundation of Hubei Province and State Key Laboratory of Functional for Informatics, Shanghai Institute of Metallurgy, Chinese Academy of Science (2001B060)Biograph: Xiong Rui (1967-), male, Associate professor, Ph. D, research direction: condensed matter physics.

Magneto-optical Disk Material for Improving the Density of Information Storage

This paper introduces the fundamental principle and features ofmagneto-optical storage technol- ogy, and discuses the trend and aseries of key techniques for increasing the data storage density ofmagneto-opti- cal disk. The three ways including MO media, recordingmethod and readout method for increasing the disk ca- pacity havebeen discussed. Moreover, the importance with the exchange-coupledeffect between the magnetic layers and recording domain morphology isemphasized.

Characterization of Bi-substituted Dysprosium Iron Garnet Films Prepared by Sol-gel Process

Bi-substituted dysprosium iron garnet films were prepared by sol-gel process, and were annealed for crystallization. The crystallographic structures of garnet films annealed at different temperatures were analyzed by XRD, the film annealed at 650℃ was polycrystalline garnet with no preferred orientation and no impurity crystalline phase. Magnetic and magneto-optical properties were investigated, the film had magnetic anisotropy perpendicular to the film plane, and exhibited strong coercivity of 1100-1600 Oe and high squareness. These films had large figures of merit applicable to magneto-optic storage, with 2 deg. at λ=430 nm and 1.5 deg. at λ=520 nm respectively.

Epitaxy growth of pure phase CeFeO_(3) thin films with high magneto-optical performance and strong vertical magnetic anisotropy

The magneto-optical effects of rare earth ferrite can be greatly improved by doping Ce^(3+)ions.CeFeO_(3)with high Ce^(3+)concentration has excellent magneto-optical properties in theory.And due to its perovskite structure it is more suitable to be deposited on the substrates of optical devices compared with the commercial garnet ferrite.In this paper,the pure phase Ce_(x)Fe_(2-x)O_(3)films were successfully obtained on the quartz glass and <100>-oriented SrTiO3crystal substrates by radio frequency magnetron sputtering.The effects of substrate and Ce:Fe ratio on the epitaxial orientation,magnetism and magnetooptical performance of films were systematically studied.For the Ce1.0Fe1.0O3/STO film,its MCD ellipticity(ψF) intensity can reach up to 4750(°)/cm in the visible band and 14090(°)/cm in near ultraviolet band.And it also shows a strong vertical magnetic anisotropy,which makes it maintain a good thermal stability when the device size is reduced.These mean that the Ce_(1.0)Fe_(1.0)O_(3)/STO film has a promising application in integrated optical communication devices.

Short-wavelength static optical recording properties of subphthalocyanine thin films

The static optical recording properties of novel bromoboron trinitro-subphthalocyanine (BTN-SubPc) thin films were studied using a self-developed short-wavelength optical disk tester with high NA objective lens. High reflectivity contrast (】30%) was obtained at low writing power (8 mW) and short writing pulsewidth (200 ns) using the Ar+ laser (514.5 nm) irradiation. These results demonstrate thatsubphthalocyanine is not only qualified for red-light recording but also a promising candidate for the recording medium of a green-light DVD-R. The leading edge, just like the falling edge, of the dye’s absorption band can also be used to realize optical disk storage if an appropriate reflector was used. It provides a new clew for double-wavelength writing/reading and choosing short-wavelength recording materials.