We have developed a simple method using a magnetic bar array to anchor nonmagnetic biomolecules for time-lapse analysis and identification. Biomolecules of interest are attached, using linker molecules, to the superparamagnetic beads which are in turn captured at gaps of the magnetic bar array. This micro-array system can be used for various studies and applications such as yeast growth studies, as illustrated in this work, and pyrosequencing. The technology is applicable to a wide variety of biomolecules using the suitable linker molecules, with the merits of low lost and reusability.

We describe a novel method for rapidly identifying and distinguishing between different DNA sequences using short tandem repeat (STR) analysis and DNA microarrays. The method can be used to deduce identity, length, and number of STRs of the target molecule. We refer to this technique as the "variable-length probe array" method for STR profiling (VLPA). The method involves hybridization of the unknown STR target sequence to a DNA microarray displaying complementary probes that vary in length to cover the range of possible STRs. A post-hybridization enzymatic digestion of the DNA hybrids is then used to selectively remove labeled single-stranded regions of DNA from the microarray surface. The number of repeats in the unknown target is then deduced based on the pattern of target DNA that remains hybridized to the array. This DNA profiling technique is useful for performing forensic analysis to uniquely identify individual humans or other species.

We present proof-of-concept experiments and modeling towards a high-sensitivity magnetic microarray which “tags” a DNA fragment (or other biological samples) with a high-moment magnetic nanoparticle (NanoTag), which is in turn detected by a high-sensitivity spin valve (SV) or magnetic tunnel junction (MTJ) detector array. The detector can count the number of magnetic tags with a resolution of 1–20 magnetic NanoTags, potentially counting individual biomolecules.

We have developed a simple elegant system based on an array of thin-film magnetic bars for creating a two-dimensional array of paramagnetic polymer beads that can be functionalized to bind fluorescently labeled DNA fragments. The resulting array can be scanned using conventional optical fluorescence instruments, to quantify the relative abundance of specific DNA sequence fragments in a biological sample. Parallel analysis for a large number of target DNA fragments is possible with such a system. The magnetic array generation system is inexpensive to fabricate, easy to use, and reusable. It has applications in DNA variation detection, pathogen detection, and DNA fingerprinting.

In this paper, the main challenges in developing a magnetic DNA microarray include: 1) The spin valve sensors must be sensitive to as few as 1-10 nanobeads to be useful for applications such as biological pathogen detection; to achieve this, the distance between the sensor and magnetic labels must be minimized. 2) The nanobeads must be monodisperse, water soluble, chemically and magnetically stable, and functionalized to attach to a DNA fragment; the nanobeads should also be superparamagnetic so that they will not agglomerate in the absence of applied fields. 3) The bio-magnetic DNA microarrays need to be designed to maximise the active sensing surface area.

Surfactants—surface additives which change surface kinetics—provide a useful additional tool for controlling the growth of thin films. A long history of work on the field has produced a sometimes conflicting view of what surfactants do, and little information exists in the particular field on non-epitaxial multilayer films. Using specular and diffuse X-ray scattering, we examine the effects of oxygen as a surfactant on multilayer Co/Cu films, and find that oxygen improves the layer-to-layer roughness correlation, while also smoothing the layers. Oxygen used at a constant background pressure of 10−8Torr has the best structural properties.

The effect of in-plane strain on the magnetic anisotropy of [110]-oriented epitaxial TbFe 2 films was studied. DC magnetron cosputtering was used to grow epitaxial TbFe 2 (110) films on A1 2 O 3 (1120) substrates with an epitaxial Nb(110) buffer layer. Torque magnetometry showed that the films had uniaxial anisotropy, and the torque curves were used to determine the magnetic anisotropy constants of the films by analyzing the rotational hysteresis loss. Film strain was measured using synchrotron radiation. The film strain and anisotropy measurements confirm that the uniaxial anisotropy results from tensile strain in the TbFe 2 (110) films. This agrees with theoretical calculations of magnetic anisotropy which show that tensile strains can induce a uniaxial anisotropy in TbFe 2 (110) films.

We have investigated the temperature-dependent growth characteristics of epitaxial Pt(111) on Al2O3(0001) using in-situ scanning tunneling microscopy. For temperatures near the onset of epitaxy (600°C), the Pt films grown by ion-beam sputtering, are flat and well-ordered. With increasing substrate deposition temperature, the surfaces grow rougher and at 700°C display island-on-island growth with up to 12 monosteps visible. When subjected to a post-deposition anneal of 950°C, the Pt becomes very smooth and the initial growth temperature becomes less important. Finally, we show that the Pt provides an excellent seed layer on which to grow and investigate metals such as Co and Cu.

We have developed a procedure for high-resolution patterning of magnetic thin films using direct-write electron beam lithography and a multistep sputter etching process [New et al., J. Vac. Sci. Technol. B 12, 3196 (1994)]. Using this patterning procedure we have defined large arrays of 0.2 by 0.4 μm magnetic islands out of a 200-Å-thick polycrystalline film of cobalt. The physical and magnetic structure of these islands has been examined using atomic and magnetic force microscopy, as well as transmission electron microscopy. Hysteresis loop measurements have been taken from large arrays of weakly interacting islands. The particles are not single domain and show considerable nonuniformity of magnetization when they are completely demagnetized. However, after application and removal of a large field along the long axes of the islands, most of the particles do relax into an almost uniform magnetization state.

We have extended the Neél model of surface anisotropy in b.c.c. crystals to include next nearest neighbor interaction. Fitting the experimental data for Fe (001) and (110) surfaces leads to some pradoxes which cast doubt on the Neél surface anisotropy as the dominant source of surface anisotropy in thin films.

Microelectrode arrays have designed using standard CAD programs utilizing a construction-set approach. The microelectrode sites, interconnect metal lines, and bond pad areas are available as predefined cells that can be recombined easily to obtain various array geometries. The microelectrodes themselves are defined by choosing the appropriate opening sizes in the passivation layer over standard metal microelectrode pads. The fabrication process used for these arrays is easily implemented with standard integrated-circuit processing equipment. It can be used stand-alone to fabricate passive arrays or added to commercial integrated-circuit processes for active arrays. Microelectrode characterization and experimental results are presented.<>

The ferromagnetic resonance frequency for films having a nonuniform magnetization is derived. It is shown that for both normal and in-plane polarizations a film in which the exchange coupling extends throughout the whole depth resonates at the same frequency as a uniform film with a magnetization $\frac{〈{M}^{2}〉}{〈M〉}$, where $M(y)$ is the depth-dependent magnetization and the angular brackets denote averages over depth. Anomalously high apparent magnetizations can result if such a film has regions of reversed magnetization.

Velocities and mobilities of Bloch and Néel domain walls in single crystal YFeO3 bars were measured using a Sixtus and Tonks transit time technique. At room temperature Bloch and Néel wall mobilities were measured to be μB=6.16×103 cm/sec‐Oe and μN=5.8×103 cm/sec‐Oe respectively. Mobilities were found to decrease monotonically and roughly linearly with increasing temperature in the temperature range 400‐600°K. These results are to be contrasted with the much higher mobilities and exponential temperature dependence of mobility for Head‐to‐Head walls where the magnetic moments on both sides of the wall are pointing Head‐to‐Head against each other. The mobilities of these three types of walls were calculated on a Walker‐like model of the moving domain wall. The results predict nearly the same mobility in all cases, assuming the same Gilbert damping parameter α. In an effort to reconcile these predictions with the experimental results we have explored the possibility of the variation of α with domain wall type by calculating the spin wave spectra of a canted antiferromagnet containing the three kinds of domain walls, but again find the results very similar for the three kinds of walls.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Ching H. Tsang, Robert L. White; Observations of domain wall velocities and mobilities in YFeO3. AIP Conf. Proc. 1 April 1975; 24 (1): 749–750. https://doi.org/10.1063/1.30271 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

For copper ferrite to assume the tetragonal phase it is necessary that more than a certain fraction of the spinel octahedral sites be occupied by Cu2+ ions. To exceed this critical occupation, copper ferrite must be nearly stoichiometric. We have established that there is a systematic relationship between copper deficiency in (Bi203/B203) flux‐grown copper ferrite and the growth temperature. In particular it is necessary to grow at low temperatures (<800°C) to obtain stoichiometric CuFe204. We have grown bulk single crystals and epitaxial films (on spinel substrates) from a stable melt at about 795°C. The bulk crystals evidence a microtwinning habit. Annealed epitaxial layers of CuFe204 display a uniaxial magnetic anisotropy with easy axis perpendicular to the films. The anisotropy is sufficiently strong (Ku?6.0×105ergs/cc) to overcome the demagnetizing effects of the thin films, suggesting that CuFe204 may have application as a bubble domain material.