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  • 1
    Electronic Resource
    Electronic Resource
    Decomposition of 1,1-Dichloroethane and 1,1-Dichloroethene in an electron beam generated plasma reactor (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 2863-2868 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An electron beam generated plasma reactor is used to decompose low concentrations (100–3000 ppm) of 1,1-dichloroethane and 1,1-dichloroethene in atmospheric pressure air streams. The energy requirements for 90% and 99% decomposition of each compound are reported as a function of inlet concentration. Dichloroethene decomposition is enhanced by a chlorine radical propagated chain reaction. The chain length of the dichloroethene reaction is estimated to increase with dichloroethene concentration from 10 at 100 ppm initial dichloroethene concentration to 30 at 3000 ppm. Both the dichloroethane and dichloroethene reactions seem to be inhibited by electron scavenging decomposition products. A simple analytic expression is proposed for fitting decomposition data where inhibition effects are important and simple first order kinetics are not observed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363945
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  • 2
    Electronic Resource
    Electronic Resource
    Thermal magnetic noise in a strip wound crystalline ferromagnetic core at 4.2 K (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 960-962 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A dc SQUID magnetometer-based system has been developed and used to measure, in the frequency range 50–2300 Hz, the complex magnetic permeability μr(ν) and the magnetization noise at 4.2 K in a strip wound toroid. This toroidal core has been made of the 3-μm-thick ribbon fabricated from a crystalline magnetically soft alloy, Ultraperm. Below 1 kHz a constant value of −arg[μr(ν)]≈2×10−3 and 1/ν shaped noise spectral density have been measured. For frequencies higher than 1 kHz a linear growth of the imaginary part μr and a white noise have been found. The noise due to the sample is found in quantitative agreement with the standard fluctuation-dissipation formula for the thermal noise, while a comparison of the permeability imaginary part magnitude with the theoretical value has indicated a partially shorted windings in the toroid, which have decreased the toroid roll-off frequency down to 1 MHz. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360879
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetic viscosity far and close to equilibrium in the superparamagnetic alloy : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5406-5408 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the simultaneous measurements of the magnetic viscosity and of the ac linear magnetic susceptibility for a sample of Cu90Co10. The magnetic viscosity S=(1/M0) [dM/d ln(t)], with M the sample magnetization and M0 the magnetization value at the beginning of the logarithmic relaxation, is measured by a standard method that involves the application to the sample of a large field step after saturation. The ac susceptibility is measured both directly at very low (≈microersteds) ac field amplitudes and from the thermal magnetization noise in the sample, the two values always being found in quantitative agreement. The imaginary susceptibility is found to be a frequency independent value χ0″(T) at low frequencies, a behavior that translates, when expressed in the time domain, to logarithmic relaxation (dM/d ln t)=(2/π)χ0″(T)H0, of the magnetization after a step excitation H0. Both S and χ0″(T) are found to be proportional to the temperature for temperatures ≤4.2 K. In addition, S and χ0″(T) are found to be of the same order of magnitude. We discuss how these results are in agreement with the idea that in both kinds of experiments one is probing an energy barrier height distribution and that, in addition, the size of the distribution involved in the "critical state,'' prepared by relaxation experiments, is of the same order of magnitude as that involved in the quasiequilibrium state probed by the ac susceptibility measurements. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362320
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  • 4
    Electronic Resource
    Electronic Resource
    Thermal equilibrium noise with 1/f spectrum in a ferromagnetic alloy: Anomalous temperature dependence : The 6th joint magnetism and magnetic materials (MMM)−intermag conferenc (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6332-6334 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the magnetization noise in a soft ferromagnetic alloy for frequencies f〈10 Hz, temperatures T〈4.2 K, and excitation field amplitudes 〈150 μA/m. The spectra agree, without any adjustable parameter, with the fluctuation dissipation formula and the measured complex susceptibility of the material. The spectra show a 1/f shape coming from a frequency-independent imaginary susceptibility χ‘0. χ‘0 is found to be proportional to T above ≈2.5 K but tends to be independent of T below this value. After annealing the sample to relieve the internal stresses, χ‘0 is found nearly temperature independent above ≈2.5 K and to sharply increase by decreasing the temperature below that value. We discuss these findings in terms of the hopping of the magnetization by activation or tunneling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358257
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  • 5
    Electronic Resource
    Electronic Resource
    Thermal equilibrium noise with 1/f spectrum and temperature-dependent magnetic viscosity in the amorphous alloy DyNi : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 5634-5636 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the magnetization noise and the imaginary susceptibility for the random anisotropy amorphous alloy DyNi1.32 for frequencies f〈10 Hz, temperatures 1.2〈T〈4.2 K, and excitation field amplitudes 〈150 μA/m (1.9 μOe). The noise spectra agree, without any adjustable parameter, with the fluctuation dissipation formula and the measured imaginary susceptibility of the material. The spectra show a 1/f shape coming from a frequency-independent imaginary susceptibility that it is found to be temperature-dependent extrapolating to zero at zero temperature. We discuss the connection between this approach and the usual relaxation experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355617
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  • 6
    Electronic Resource
    Electronic Resource
    Thermal magnetization noise as a function of frequency in amorphous ferromagnets (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 5984-5987 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the observation of 1/frequency magnetization noise in toroidal strip-wound cores of amorphous ferromagnetic alloys at liquid-helium temperatures and in the frequency range 0.1 Hz–1 kHz. The materials tested are Co-based alloys, and exhibit very low magnetostriction and good soft magnetic properties. The experimental apparatus consists of a radio frequency SQUID magnetometer coupled to the sample by a superconducting flux transformer which is devised to allow measurements of its complex inductance. We show that the magnetization noise obeys in detail the fluctuation-dissipation theorem. A temperature-dependent partial roll-off of the complex permeability is found at ∼100 Hz, possibly linked to pinning wells for domain-wall motion. The link between 1/frequency noise and magnetic viscosity is briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343626
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  • 7
    Electronic Resource
    Electronic Resource
    Thermal magnetic noise in rf SQUIDS coupled to ferromagnetic cores (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 2130-2136 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a simple model for the thermal magnetic noise in a rf SQUID coupled to a ferromagnetic core via a superconducting dc flux transformer. We show that, under conditions that are almost always fulfilled in practice, the coupling to the core can be described in terms of a SQUID frequency-dependent complex inductance Ls (ω). This inductance reduces to an ordinary, frequency-independent real value above a roll-off frequency ωc . To this inductance, a Nyquist flux noise generator is associated, with spectral density S'2cursive-phii(ω) =−4kBT Im[Ls(ω)]/ ω, where kB is the Boltzmann constant, T the temperature, and Im[Ls (ω)] the imaginary part of Ls (ω). If ωc (very-much-less-than)ωrf , with ωrf the frequency of the rf pump, then the response of the SQUID to low-frequency signals is not modified by the coupling to the core, while the above Nyquist noise acts as an additive input noise. We experimentally demonstrate the model for a SQUID coupled to a toroidal core.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342862
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  • 8
    Electronic Resource
    Electronic Resource
    Low temperature properties of soft magnetic materials: Magnetic viscosity and 1/f thermal noise : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5363-5365 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study the magnetic properties of soft ferromagnetic cores in the low field linear regime at low temperature (T≤4.2 K) in view of their use in connection with superconducting quantum interference device magnetometers. We have tested several amorphous and polycrystalline alloys in the form of strip-wound toroidal cores. Both high and near zero magnetostrictive alloys are studied. All samples are found out to be the source of thermal magnetic noise of 1/f spectral density in agreement with the fluctuation dissipation theorem. This type of thermal noise comes from a frequency independent imaginary permeability. This feature is equivalently described in terms of the magnetic viscosity effect or by considering the constant (residual) term in the classical Legg's equation of magnetic losses at low fields. Measurements on a few Co-based amorphous alloys show that the magnetic viscosity is independent of temperature. Explanations in terms of thermal activation processes and quantum tunneling are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353732
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  • 9
    Electronic Resource
    Electronic Resource
    Thermal 1/f noise in Cu90Co10: Effect of grain size : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 3975-3977 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the thermal magnetic noise with 1/f spectrum and the related ac linear response susceptibility measured at liquid helium temperatures in the bulk granular system Cu90Co10. The thermal magnetic noise and the related linear response, ac susceptibility have been shown to be the close analogue at thermal equilibrium of the magnetic viscosity. The measurements have been performed on a set of samples where various size distributions of the nanostructured magnetic clusters have been produced by annealing the ribbons by the Joule heating technique. The thermal equilibrium, low temperature magnetic viscosity has been found to depend on the heating current in the same way as the room temperature giant magnetoresistance. We discuss how this analogy relates magnetic viscosity to the barrier energy distribution resulting from grain size distribution. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364911
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  • 10
    Electronic Resource
    Electronic Resource
    Thermal magnetic noise due to eddy currents in a strip wound ferromagnetic core at 4.2 K (abstract) : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6996-6996 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Many applications involving high impedance signal sources and use of the low input impedance SQUID magnetometer would take advantage of the use of low noise ferromagnetic cores in matching transformers. Noise in ferromagnetic cores at liquid helium temperatures has been shown to be limited by thermal fluctuation of the magnetization for the two following cases: for bulk cores, where the skin effect sets a low frequency (〈100 Hz) roll-off of the effective permeability, and the spectral density is white up to the roll-off, and for strip wound cores at frequencies lower than ≈100 Hz, where magnetic viscosity gives origin to a frequency independent imaginary permeability and correspondingly to a 1/ω shaped spectral density. Thanks to a high sensitivity dc SQUID magnetometer we have now been able to measure thermal noise due to the skin effect in a strip wound 15-μm-thick Ultraperm core where the roll-off frequency is ≈1 MHz. Data for the noise are in quite quantitative agreement with the prediction of the fluctuation dissipation formula and the measured values of μ(ω). At frequencies lower than a corner ≈1 kHz the noise is again dominated by the 1/ω tail due to magnetic viscosity. We discuss the relevance for applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356753
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