Comparative analysis of thin Ni and CoNiMnP magnetic films

The results of an investigation of thin Ni and CoNiMnP films deposited by electroplating over polyurethane-acrylate flexible substrates are presented. To improve magnetic properties of the films, an electroplating process was carried out with assistance of a strong magnetic field (3900 G). The evaluated film properties were coercivity, remanence, maximum energy product, adherence and film composition. Comparison between the magnetic properties of the samples has shown that Ni and CoNiMnP films are suitable for distinct areas of applications in micro-devices: vibrating diaphragms and micro-magnet machines, respectively.     

Periodically structured glancing angle deposition thin films

Thin films fabricated using the glancing angle deposition technique have a porous microstructure consisting of freestanding columns. Many promising applications of such thin films require that the columns be arranged in periodic arrays using substrate topographies-so-called seed layers-that enforce controlled film nucleation. In this paper, we present the optimized design, fabrication, and characteristics of periodically structured thin films, achieving highly uniform periodic film morphologies. We derive geometrical rules for designing substrate seed layers, and explain how to fabricate large area seed patterns with submicrometer features. Using negative-resist electron-beam lithography and laser direct write lithography, we have reached extremely high pattern densities. An experimental analysis is provided of seed-enforced nucleation and thin-film growth, showing that the elimination of film growth between seeds is crucial, and that the substrate seed layer geometry must match the intended film microstructure. Finally, we discuss the enhanced properties of periodically structured oblique angle thin films and their applications.     

Charged walls in thin magnetic films

Charged walls are domain walls which carry a net "magnetic charge" (div M) due to their orientation relative to the domain magnetizations. They differ from ordinary Bloch and Néel walls (which are uncharged) primarily in their much wider profile. In order to calculate such walls, a variational method was developed. It is based on the separation of that part of stray field energy which would be present even with an infinitely thin wall. The main results of the calculations are as follows. 1) Isolated charged walls do exist if exchange energy is taken into account, as opposed to the periodic solution known for the limit of negligible exchange energy. 2) Rotated, partially charged walls develop a Néel-wall-like narrow core region. Detailed results for the wall profiles, energies and widths as a function of wall angle, orientation, film thickness, and material parameters are presented. They are applied to two examples: the case of a Permalloy film in a domain tip propagation memory, and the case of the implanted layer on a contiguous disk bubble device.     

Astroid plotter for thin magnetic films

The rotational astroid of uniaxial thin films may be obtained from the cross-field loopm_{x} , h_{y}graphically or electronically by assuming Slenczewski's tangent rule. The graphical construction by means of the tangent rule is demonstrated. The derivation of the transformation to obtain the astroid electronically is given, and a comparison is made with astroids obtained graphically as well as those obtained by direct static measurements. An astroid plotter has been constructed using standard analog computer components in conjunction with a Kerr apparatus. The resulting displays give the entire rotational astroid and completely avoid wall switching and blocking phenomena. Examples are shown of applications of the astroid plotter with particular emphasis on obtaining the influence of bit geometry for all orientations of magnetization.     

Hard magnetic two-phase Co-Cu thin films

The magnetic properties of sputtered films of 25 Co-75 Cu and 50 Co-50 Cu before and after annealing were investigated. In the as-sputtered state the films exhibit the structure of a metastable fcc solid solution. Annealing at 500 to 700°C causes decomposition into two phases, Cu and fcc 89 Co-11 Cu. The decomposition supposedly occurs by heterogeneous nucleation at the grain boundaries, and growth by grain boundary diffusion. The 89 Co-11 Cu phase exists in the form of small particles with magnetic single domain behavior. The films have coercivities up to 280 Oe. Squareness ratios between 0.7 and 0.9 were found. No strain sensitivity of the magnetic properties could be detected. This material is regarded to be suitable for magnetic recording.     

Pulse switching in thin magnetic films

The main results of the investigations of pulse switching in thin magnetic films with uniaxial anisotropy which have been obtained in Moscow State University are reviewed. Simultaneous investigation of integral switching properties, inner effective field, and dynamic domains produced during pulse switching has increased our understanding of bi-directional incoherent rotation mechanism and found new peculiarities of the pulse switching by domain boundary propagation. A new variety of incoherent rotation which manifests itself at strong fields has been found. It has been also found that the curve representing the pulse field dependence of an inverse switching time in the general case consists of five distinct regions. The relation between these regions and the switching mechanisms are discussed.     

Electroless deposition of CoPtWP magnetic thin films

CoPtWP magnetic thin films were prepared by electroless deposition. The influence of bath pH, deposition temperature and bath composition on the deposition speed, alloy content, microstructure, and magnetic properties of CoPtWP thin films were investigated. It was found that deposition speed increased gradually with the bath pH and deposition temperature. The cobalt content in the CoPtWP thin films varied from 77 at.% to 85 at.% by controlling the bath pH. The microstructure of CoPtWP thin films was dependent on bath pH and deposition temperature: two mixed structures, face centered cubic (fcc) and hexagonal close packed (hcp), were observed at low pH values and low deposition temperature. With the increase of pH values and deposition temperature, the intensity of fcc (111) peak suppressed gradually. The surface morphology was markedly influenced by bath pH, deposition temperature and bath composition. VSM and MFM measurements revealed that perpendicular coercivity had been increased with the bath pH. Unique hard magnetic properties of CoPtWP thin films with large perpendicular magnetic anisotropy were obtained at 90 °C and bath pH 13.0.     

The electron states of one-dimensional thin metal films

We present a detailed numerical study of the electronic states of a finite one-dimensional array of δ function potentials bounded by square surface barriers which may or may not be symmetrical. We study in particular the surface density of states and its dependence on the surface barriers and on the thickness of the specimen.     

Scanning electron microscopy and electron microprobe analysis of Au-GeOx-Cu and Au-AlOx-Cu sandwich structures

Direct observations of the counter-electrode surface of electroformed Au-I-Cu sandwich structures (where I is reactively evaporated AlO _x or GeO _x ) were carried out using scanning electron microscopy. Electron microprobe analyses of surface defects in electroformed samples, after etching the copper counter-electrode, tended to confirm the presence of copper. Surface defects are identified as the terminations of filament bundles, which supports the filamentary model of conduction.     

Analytical electron microscopy of thin films and interfaces

In this paper a brief overview is presented of some of the techniques available with transmission electron microscopy (TEM) to characterize thin films and interfaces. The critical role that sample preparation plays is discussed. Examples of the application of many of the analytical techniques used in TEM are given. These include nano area electron diffraction, energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy. High resolution imaging is available at atomic resolution and new methods are being developed to analyze the images including computer simulation. Imaging of magnetic domains is important to the study of materials used in digital data storage.     

Transmission electron microscopy of nanocomposite CrB-N thin films

This paper reports on the preparation and characterization of CrBN nanocomposite coatings for low friction, low wear and high thermostability applications. Sputtered CrBN thin films were prepared in order to obtain a composite structure consisting of hard CrB₂ and CrN crystallites as well as hexagonal BN lubricant phase by unbalanced magnetron sputtering (UBM) of a CrB₂ target in an Ar/N₂ gas discharge. Coatings, with a total thickness of 4.5-5.5 μm, were deposited at 450 °C on silicon single-crystal substrates. A nanocomposite structure was obtained by increasing the nitrogen content of the sputtering gas. The coating microstructure was investigated on selected samples by high-resolution transmission electron microscopy. The films were generally found to consist of crystallites of a 1-4 nm size embedded in amorphous matrix. This crystalline phase was identified by electron diffraction as hexagonal CrB₂ for low nitrogen content and cubic CrN for high nitrogen content. In the medium composition range, the structure was amorphous, still keeping the two-phase morphology. The use of high-resolution imaging mode helped to reveal the composition of the amorphous phase which seems predominantly to consist of boron nitride.     

On debonding of thin films

Debonding of a thin film from a large substrate is analyzed by an interface crack model. Based on a solution to interface cracks given by the author, energy release rate and stress intensity factors at the interface crack between the film and the substrate under general film edge loads are determined analytically. The solution is favorably compared with the result from the literature. Thermal stress intensities due to a uniform temperature change are also considered. The solution may be helpful for the analysis and testing of thin film debondings.     

WO3纳米薄膜的制备与气致变色特性研究

报道了以钨粉为原料，采用溶胶一凝胶技术和旋转镀膜方法，制备出了气致变色WO3纳米薄膜。采用椭偏仪、X射线衍射仪(XRD)、场发射扫描电子显微镜(FE-SEM)、红外光谱仪以及可见光分光光度计等方法分析了薄膜的特性。研究结果表明热处理使得薄膜致密，折射率增大，厚度减小，薄膜结晶；过氧键消失，WO3微结构发生了变化，共角W-O-W键吸收越来越强，且向高波数方向移动。这些变化归因于热处理导致的WO3颗粒形状、团聚状态的变化以及应变键的产生。WO3纳米薄膜具有很好的气致变色特性，致色与退色态透射率变化超过60％，变色起因于H扩散到WO3薄膜中形成的小极化子吸收。     

Magnetochromatic effects in magnetic fluid thin films

A homogeneous ferrofluid composition capable of reversiblyforming ordered crystalline two-dimensional hexagonal lattices ofmagnetic particle columns in a thin film under the influence ofexternal magnetic fields has been synthesized. We can manipulatethe spacings between the particles columns by adjusting parameters suchas external magnetic field strength, film thickness, rate of change ofthe field strength, and concentration of magnetic particles in theferrofluid. These spacings between particle columns are of theorder of several micrometers and are capable of diffracting visiblelight to produce monochromatic interference colors. We can changethe resulting colors by altering the lattice spacing to exhibit thefeasibility of generating monochromatic colors.