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  • 2000-2004  (18)
  • 1995-1999  (35)
  • 1975-1979  (17)
  • 1
    Electronic Resource
    Electronic Resource
    Exchange interactions in (FeT)90Zr10(T=Ru,Mn) metallic glasses (abstract) : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 5282-5282 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recently there have been several theoretical reports about models of amorphous transition metal alloys which take into account the fluctuations of local magnetic moments due to structural disorder.12 It is predicted that the local atomic moment on an atom depends on the number of first near neighbors with short distances (contracted atoms) and it could be positive, negative, or negligible. An amorphous Fe–Zr system could be a typical system to study these features which have a key role in determining the magnetic structure. Fe90Zr10 orders ferromagnetically at 230 K and exhibits a mixed state at T〈30 K showing spin glasslike behavior. Here we present the results on Mn and Ru substitution for Fe in Fe90Zr10. Mn is known to couple antiferromagnetically (AF) to Fe while Ru is expected to be nonmagnetic. We find that Mn reduces the Curie temperature (Tc) gradually while the spin freezing temperature (Tf) remains nearly constant. However, in the case of Ru, Tf drastically increases and 5 at. % Ru drives the system to a clear spin glass state. Hyperfine field studies show gradual evolution of AF coupled spins and their distribution, pointing out the existence of a well defined bimodal distribution. Fe–Fe exchange is believed to become antiferromagnetic for Fe–Fe distances 〈0.15 nm and the possible occurrence of short Fe–Fe distances in an amorphous matrix is often cited as the reason for the competing interactions to occur. However, Ru with a larger atomic size should have resulted in long Fe–Fe distance (which we have found in crystalline Fe2Zr which is a closed packed structure3). We propose that the dilution of Fe moment and the band modifications due to Ru substitution seemed to promote antiferromagnetic coupling in a Fe–Zr system. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364571
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  • 2
    Electronic Resource
    Electronic Resource
    Structural and transport properties of (Bi,Pb)4Sr3Ca3Cu4−mFemOx (m=0–0.06) glasses: Precursors for high Tc superconductors (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 2954-2961 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Microstructure and transport properties (between 80–450 K) of the Fe doped as-quenched Bi3Pb1Sr3Ca3Cu4−mFemOx (m=0.0, 0.02, 0.04, 0.05, and 0.06) type multicomponent glassy precursors for high-temperature superconductors were first reported in this paper. It has been shown from x-ray diffraction, scanning electron microscopy, thermal analysis, density, and oxygen molar volume measurements that single phase homogeneous glasses are formed. Even with small addition of Fe, a large change of glass transition temperature (Tg) indicates appreciable change of glass network structure of the undoped (Bi,Pb)4Sr3Ca3Cu4Ox glass which is reflected in the properties of the corresponding high-temperature annealed glass termed as glass-ceramic (GC) samples. These GC samples are found to be superconductors. Addition of Fe is considered to break up some of the original Cu–O–Cu bonds forming some new Cu–O–Fe and Fe–O–Fe type bonds. A nonlinearity (increase) in the dc conductivity (σdc) of the as-quenched glass sample is observed around m=0.02. This increase of dc conductivity is ascribed to be due to the additional hopping between Fe2+ and Fe3+ which finally destroys superconductivity for m≥0.06. This is also responsible for the nonlinear variation of activation energy of the Fe doped glass and hence change in the superconducting properties of the glass ceramics. The high temperature (above θD/2, θD being the Debye temperature) σdc data of the glasses were explained by considering small polaron hopping conduction mechanism. The dc conductivity of these glasses are found to follow Greaves' variable range hopping model in the intermediate range of temperature. The polaron hopping model of Schnakenberg and Emin can predict the conductivity data in the high-temperature regime. All the Fe-doped glass ceramics showed superconducting transitions with Tc between 100 and 110 K. The corresponding zero resistance temperature, Tco which is maximum (79 K) for m=0, decreases consistently with increase of Fe-concentration and finally superconducting behavior is destroyed for m≥0.06. This behavior is consistent with-pair breaking mechanism. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475682
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  • 3
    Electronic Resource
    Electronic Resource
    Women's perceptions of decision-making about hysterectomy (2004)
    Oxford, UK and Malden, USA : Blackwell Publishing Ltd
    BJOG 111 (2004), S. 0 
    Details
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Objective  To explore women's views of decision-making relating to hysterectomy.Design  Structured questionnaire and in-depth interview surveys.Setting  A teaching hospital and a district general hospital in northeast Scotland.Sample  Women scheduled for hysterectomy for benign menstrual problems.Methods  Pre-operative questionnaires were sent to a consecutive sample of women booked for hysterectomy. A purposive sample was interviewed post-operatively.Main outcome measures  Women's experiences of, and satisfaction with, information provision, communication and decision-making processes; the relationship between views of decision-making processes and decisions made.Results  One hundred and four women (66%) returned questionnaires. Most responded positively to structured questions about the process by which the decision to have a hysterectomy was reached. Almost all (97%) reported satisfaction with the decision made. Twenty women were interviewed post-operatively. A number, including some who had responded positively on the questionnaire, described aspects of the decision-making process that were suboptimal. Women's perceptions of the decision-making process, including the way their doctors communicated with them, did impinge on their views of the course of action selected. Some women had residual doubts about the appropriateness of hysterectomy.Conclusions  In a significant minority of women, there are important shortcomings in current patterns of information provision and communication relating to decision-making. These are unlikely to be picked up by conventional structured patient feedback surveys. Further efforts are required to ensure that women are adequately informed and involved in decisions about gynaecological treatments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-0528.2003.00027.x
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  • 4
    Electronic Resource
    Electronic Resource
    Multiphonon hopping conduction in nonconventional chromium-doped Bi3Pb1Sr3Ca3Cu4−nCrnOx (n=0.025–0.2) glasses with nanocrystalline particles and clusters (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 5033-5042 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transport properties of Cr containing multicomponent oxide glasses Bi3Pb1Sr3Ca3Cu4−nCrnOx (n=0.025, 0.05, 0.1, and 0.2) dispersed with nanocrystalline particles (5–20 nm depending on the values of n) have been reported in the temperature range of 250–450 K. Conductivity of this glass-nanocrystal composite system shows little decrease with increasing Cr content. Above θD/2 (θD is the Debye temperature), conductivity data can be analyzed with small polaron hopping models. Interestingly, unlike undoped Bi4Sr3Ca3Cu4Ox (or Bi-4334) glasses [showing nonadiabatic small polaron hopping (SPH) conduction at T〉θD/2], the Cr doped glasses supports adiabatic SPH conduction mechanism above θD/2 indicating change of glass network structure due to partial substitution of Cu by Cr. But below this temperature Mott's or Greaves' variable range hopping models can be consistently used to fit the experimental conductivity data only with larger (compared to the usual transition metal oxide glasses) values of the density of states at the Fermi level N(EF). The most probable transport mechanism for the entire range of temperature and glass compositions is concluded to be due to multiphonon tunneling of large polarons between the nanoclusters present in the glasses which is also in sharp contrast to the behavior of the undoped (Bi-4334) glass. All the glass samples (except n≥0.2) are found to become superconductors by annealing at higher temperatures. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1317237
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  • 5
    Electronic Resource
    Electronic Resource
    Particle size and magnetic field dependent resistivity and thermoelectric power of La0.5Pb0.5MnO3 above and below metal–insulator transition (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5125-5134 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of particle size on the transport properties (resistivity and thermopower) of La0.5Pb0.5MnO3 has been investigated both in the presence and in the absence of magnetic field B=0.0–1.5 T (maximum). Grain size, dc conductivity; and the metal–insulator transition temperature Tp of the sample increase with increasing annealing time. Grain size has, however, comparatively little effect on the Seebeck coefficient S. Magnetoresistance is higher for the samples with smaller grain sizes. dc magnetic susceptibility also increases with increasing grain size. High temperature (T〉θD/2) resistivity data well fit the small polaron hopping model. Polaron hopping energy WH decreases but polaron radius rp increases with the increase of grain size. In the metallic regime (for T〈Tp), resistivity data fit well with ρ=ρ0+ρ2.5 T2.5 and the transport mechanism is attributed mainly to the magnon-carrier scattering (∼T2.5). In all the samples with different grain sizes, S changes sign below Tp. In contrast to magnetoresistance, application of magnetic field increases S at low temperature (T〈Tp) for these samples. Thermopower data in the metallic phase (both for B=0.0 and 1.5 T) can be analyzed by considering a spin-wave fluctuation term (∼T4) in addition to the magnon-scattering term similar to the case of resistivity data. Although the variable range hopping mechanism is supported from the resistivity data (for Tp〉T〉θD/2), it is hard to justify this model from the temperature dependent thermopower data. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1459618
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  • 6
    Electronic Resource
    Electronic Resource
    Grain structure effects on the lattice thermal conductivity of Ti-based half-Heusler alloys (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 43-45 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Half-Heusler alloys with the general formula TiNiSn1−xSbx are currently being investigated for their potential as thermoelectric (TE) materials. A systematic investigation of the effect of Sb doping on the Sn site and Zr doping on the Ti site on the electrical and thermal transport of the TiNiSn system has been performed. Unexpectedly, lattice thermal conductivity κL appears to increase somewhat randomly with small amounts (x〈5%) of Sb doping. Subsequently, an investigation of grain structure in these Sb-doped materials has been found to correlate with the anomalous behavior of κL. Furthermore, effects of submicron grain sizes on κL in ball milled and shock compressed samples are also presented. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1488698
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of Sb doping on the thermoelectric properties of Ti-based half-Heusler compounds, TiNiSn1−xSbx (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 2476-2478 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Half-Heusler alloys (MgAgAs type) with the general formula MNiSn where M is a group IV transition metal (Hf, Zr, or Ti) are currently under investigation for potential thermoelectric materials. These materials exhibit a high negative thermopower (−40 to −250 μV/K) and low electrical resistivity values (0.1–8 mΩ cm) both of which are necessary for a potential thermoelectric material. Results are presented in this letter regarding the effect of Sb doping on the Sn site (TiNiSn1−xSbx). The Sb doping leads to a relatively large power factor of (0.2–1.0) W/m K at room temperature for small concentrations of Sb. These values are comparable to that of Bi2Te3 alloys, which are the current state-of-the-art thermoelectric materials. The power factor is much larger at T(approximate)650 K where it is over 4 W/m K making these materials very attractive for potential power generation considerations. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1318237
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  • 8
    Electronic Resource
    Electronic Resource
    High figure of merit in Eu-filled CoSb3-based skutterudites (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 598-600 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report measurements of electrical resistivity, thermopower, thermal conductivity, and Hall coefficient of polycrystalline Eu-doped CoSb3-based skutterudites with compositions Eu0.20Co4Sb12, Eu0.43Co4Sb11.59Ge0.31, and Eu0.42Co4Sb11.37Ge0.50. The relatively high mobility of these compounds, as compared to that of La- and Ce-filled skutterudites, may play a role in the large thermoelectric figure of merit (ZT〉1 at 700 K) of Eu0.42Co4Sb11.37Ge0.50. We discuss the significant potential of these compounds for thermoelectric applications. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1433911
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  • 9
    Electronic Resource
    Electronic Resource
    Depoling a ferroelectric capacitor (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 3373-3375 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A "shrinking hysteresis loop" method, analogous to degaussing a ferromagnet, is used to depolarize a ferroelectric thin film and reach the origin, nominally the zero polarization-zero applied field state. Scanning piezoresponse imaging of the depoled state shows fragmentation into domains of up and down polarization that constitute the zero polarization state. Furthermore, the depoling method improves the left–right symmetry of the coercive field in "imprinted" samples. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1476063
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  • 10
    Electronic Resource
    Electronic Resource
    Anomalous optical response of Nd1.85Ce0.15CuO4−y superconducting thin films (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1989-1991 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A study of the normal state optical response of epitaxial thin films of electron doped superconductor Nd1.85Ce0.15CuO4−y is reported. The normal state optical response of these films were not proportional to the temperature derivative of the resistance of the films as expected by a bolometric model and as seen in p-type superconductors such as YBa2Cu3O7−δ. The normal state optical response of the films with different transition temperatures were also remarkably different from each other. The observation of anomalous optical response is attributed to the possible presence of photoconductivity in Nd1.85Ce0.15CuO4−y. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113300
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