Influence of the strain effect on magnetocrystalline anisotropy in Co2Fe0.4Mn0.6Si Heusler alloys.

The perpendicular magnetocrystalline anisotropy, magnetoelastic properties as well as the Gilbert damping factor in Co2Fe0.4Mn0.6Si thin films were found to depend on a magnetic layer thickness, and they can be also tuned by the application of additional Ag buffer layer. The tetragonal distortion of a magnetic layer was found to increase with decreasing thickness, and after the application of an additional Ag buffer layer, the character of this distortion was changed from tensile to compressive in the plane of a film. A correlation between the tetragonal distortion and perpendicular magnetocrystalline anisotropy was found. However, the magnitude of the observed tetragonal distortion for most samples seems to be too small to explain alone the experimentally found large magnitude of the perpendicular magnetocrystalline anisotropy. For these samples, other mechanisms including both surface and volume effects must be taken into account.

Rigorous ESR spectroscopy of Fe3+ impurity ion with oxygen vacancy in ferroelectric SrTiO3 crystal at 20 mK.

Impurity Fe3+ ion electron spin resonance (ESR) spectroscopy using multiple dielectric modes in a SrTiO3 dielectric resonator has been performed with a tunable DC magnetic field of up to 1.6 T. The Ti[Formula: see text] ion is substituted by Fe3+ ion forming FeO6 octahedral complex with an iron-oxygen-vacancy (Fe[Formula: see text]). In such a metal-ligand complex, a giant g-factor of [Formula: see text] was observed in the ferroelectric phase at 20 mK. The change of Fe3+ ion center-symmetry in the FeO6 complex as a soft-mode characteristics of ferroelectric phase transition and the influences of iron-oxygen-vacancy (Fe[Formula: see text]), are interactively sensitive to asymmetry in the octahedral rotational parameter Φ in SrTiO3.

Aggregate frequency width, nuclear hyperfine coupling and Jahn-Teller effect of Cu2+ impurity ion ESR in SrLaAlO4 dielectric resonator at 20 millikelvin.

The impurity paramagnetic ion, [Formula: see text] substitutes Al in the [Formula: see text] single crystal lattice, this results in a [Formula: see text] elongated octahedron, and the resulting measured g-factors satisfy four-fold axes variation condition. The aggregate frequency width of the electron spin resonance with the required minimum level of impurity concentration has been evaluated in this single crystal [Formula: see text] at 20 millikelvin. Measured parallel hyperfine constants, [Formula: see text], were determined to be [Formula: see text] and [Formula: see text] at [Formula: see text] for the nuclear magnetic quantum number [Formula: see text], and [Formula: see text] respectively. The anisotropy of the hyperfine structure reveals the characteristics of the static Jahn-Teller effect. The second-order-anisotropy term, [Formula: see text], is significant and cannot be disregarded, with the local strain dominating over the observed Zeeman-anisotropy-energy difference. The Bohr electron magneton, [Formula: see text], (within [Formula: see text] so-called experimental error) has been found using the measured spin-Hamiltonian parameters. Measured nuclear dipolar hyperfine structure parameter [Formula: see text] shows that the mean inverse third power of the electron distance from the nucleus is [Formula: see text] a.u. for [Formula: see text] ion in the substituted [Formula: see text] ion site assuming nuclear electric quadruple moment [Formula: see text] barn.

Whispering Gallery mode ESR spectroscopy and parameters measurement in single crystal SrLaAlO4 at millikelvin temperature.

A cylindrical single crystal SrLaAlO4 Whispering Gallery mode dielectric resonator was cooled to millikelvin temperature using a dilution refrigerator. By controlling a DC-magnetic field, impurity ions' spins were coupled to a variety of modes allowing the measurement of hybrid spin-photon systems. This Electron Spin Resonance mapping technique allowed us to detect Cu2+,Fe3+ and Mn4+ impurity ions (at the level of parts per million (ppm) to parts per billion (ppb)), verified by the measurement of the spin parameters along with their site symmetry. Whispering Gallery modes exhibited Q-factors ⩾105 at a temperature less than 20mK, allowing sensitive spectroscopy with high precision. Measured hyperfine line constants of the Cu2+ ion shows different parallel g-factors, g‖Cu, of 2.526,2.375,2.246 and 2.142. The spin-orbit coupling constant of the Cu2+ ion was determined to be λ≃-635cm-1. The low-spin state Fe3+ ion's measured parallel g-factor, g‖Fe, of 2.028 reveals tetragonal anisotropy. The Mn4+ ion is identified in the lattice, producing hyperfine structure with high-valued g-factors,g‖Mn, of 7.789,7.745,7.688,7.613,7.5304 and 7.446. The hyperfine structures of the Cu2+ and Mn4+ ions show broadening of about 79G between 9.072GHz and 10.631GHz, and 24.5G broadening between 9.072GHz and 14.871GHz, respectively.

Graphene epitaxy by chemical vapor deposition on SiC.

We demonstrate the growth of high quality graphene layers by chemical vapor deposition (CVD) on insulating and conductive SiC substrates. This method provides key advantages over the well-developed epitaxial graphene growth by Si sublimation that has been known for decades. (1) CVD growth is much less sensitive to SiC surface defects resulting in high electron mobilities of ∼1800 cm(2)/(V s) and enables the controlled synthesis of a determined number of graphene layers with a defined doping level. The high quality of graphene is evidenced by a unique combination of angle-resolved photoemission spectroscopy, Raman spectroscopy, transport measurements, scanning tunneling microscopy and ellipsometry. Our measurements indicate that CVD grown graphene is under less compressive strain than its epitaxial counterpart and confirms the existence of an electronic energy band gap. These features are essential for future applications of graphene electronics based on wafer scale graphene growth.

Frequency-temperature compensation in Ti(3+) and Ti(4+ ) doped sapphire whispering gallery mode resonators.

A new method of compensating the frequency-temperature dependence of high-and monolithic sapphire dielectric resonators near liquid nitrogen temperature is presented. This is achieved by doping monocrystalline sapphire with Ti(3+) ions. This technique offers significant advantages over other methods.

High-Q sapphire-rutile frequency-temperature compensated microwave dielectric resonators.

A sapphiro-rutile composite resonator was constructed from a cylindrical sapphire monocrystal with two thin disks of monocrystal rutile held tightly against the ends. Because rutile exhibits low loss and an opposite temperature coefficient of permittivity to sapphire, it is an ideal material for compensating the frequency-temperature dependence of a sapphire resonator. Most of the electromagnetic modes in the composite structure exhibited turning points (or compensation points) in the frequency-temperature characteristic. The temperatures of compensation for the WG quasi TM modes were measured to be below 90 K with Q-factors of the order of a few million depending on the mode. For WG quasi TE modes, the temperatures of compensation were measured to be between 100 to 160 K with Q-factors of the order of a few hundreds of thousands, depending on the mode. The second derivatives of the compensation points were measured to be of the order 0.1 ppm/K(2 ), which agreed well with the predicted values.

Simultaneous quantification of c-myc oncoprotein, total cellular protein, and DNA content using multiparameter flow cytometry.

Variations in total cellular protein content can confound interpretation of the significance of modulations of specific cellular proteins. In an effort to overcome this problem, a technique is described for the simultaneous measurement of a specific cellular protein, total cellular protein, and DNA content. The method utilizes dual-laser (uv and 488 nm) excitation and three fluorescent dyes: FITC, SR101, and DAPI. FITC-labelled antibody coupled with indirect immunofluorescence was used to quantify the c-myc oncoprotein, whereas SR101 and DAPI were used to measure total cellular protein and cellular DNA, respectively. Flow cytometric measurements of c-myc oncoprotein were compared to densitometric readings of p64c-myc. SR101 protein determinations were compared to those obtained by the Lowry technique. Results indicated that flow cytometric measurements correlated well with those obtained by the biochemical methods. The usefulness of the technique was further examined following treatment of exponentially growing HL-60 cells with 2.5 micrograms/ml cycloheximide for 0 to 12 h. Cycloheximide treatment was found to cause a significant decrease in c-myc oncoprotein content within 2 h (P less than 0.05), a relative increase in the proportion of G0/G1 cells and a modest decrease in total cellular protein. This technique appears to provide a rapid, quantitative approach, useful for investigating alterations in cellular growth balance occurring with cell differentiation, neoplastic transformation, or cell treatment with radiation or cytostatic drugs.

Development and exploratory trials of a cognitive preference inventory for medical students.

A medical cognitive preference inventory was developed and tested with two samples, one in Israel and the other in the United States. Acceptable levels of internal consistency of the whole test and of its three subtests were demonstrated. Direct and indirect evidence for the validity of the test was provided. The potential uses of the test for student selection and evaluation as well as for programme evaluation were discussed. Two forms, E and F, each consisting of eighteen items, are recommended for use with medical students. A combination of these two forms is designed as form G. Administration of one form to half of a sample and the other form to the other half, followed by pooling the individual scores, thereby obtaining results comparable to those of form G, is recommended when time to administer the inventory is limited.

Artifactual midline cervical defect seen during myelography.

A case of ventral extradural cervical defect produced by extension during myelography is reported. The defect simulated a herniated cervical disc. This phenomenon has been reported in the lumbar area, but not in the cervical region. The etiology is discussed.