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  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Linear magnetic birefringence Δnm was used to study the concentration dependence of both the total magnetic specific heat Cm and critical amplitudes in the random exchange Ising model (REIM) system FexZn1−xF2. We find the proportionality between Δnm and the magnetic energy Um is x independent for 0.24≤x≤1.0, since Δnm scales with x2 as does Um. However, the critical part of Cm is found to decrease with dilution very much faster than x2. To explain this, a scaling form is derived which describes the x-dependent crossover from pure Ising to REIM with a crossover exponent φ=α, the pure Ising specific heat exponent. The critical amplitudes A± of Cm = A±||t − tn||−α˜ are shown to scale as A±(x)A±(x)∼ (1 − x)(α˜−α)/(φ)∼ (1 − x)−1.9(3), using the experimental REIM value of α˜=−0.09(3), and theoretical value of α=0.105(7). Good agreement between theory and experiment is found.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5518-5520 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Standing-spin-wave resonance (SSWR) modes have been observed in an antiferromagnet for the first time. The experiments were performed on MnF2 films of thicknesses t=0.98 and 0.23 μm, grown epitaxially on carefully polished (001) Mn0.99Fe0.01F2 substrates. An intervening 1.0-μm-thick homoepitaxial, buffer layer of Mn0.99Fe0.01F2 was first deposited to improve both the epitaxial growth and thickness uniformity of the final MnF2 film. The observed SSWR modes exhibit spacings ΔHn appropriate to the boundary conditions in which the spins are pinned at both interfaces. From the spacings of the modes, a value of the spin-wave stiffness constant is obtained which is in good agreement with the calculated value from the known exchange and anisotropy interactions of bulk MnF2.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3291-3293 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The quasielastic scattering of neutrons in d=3 (Fe0.6Zn0.4F2) and d=2 (Rb2Co0.85Mg0.15F4) random-field Ising model (RFIM) systems in the critical region has been studied. A sharp phase transition at Tc(H) with new critical behavior is observed at d=3 whereas the phase transition is destroyed at d=2 in the presence of a random field. At d=3 the antiferromagnetic state is stable for all T and H below Tc(H) whereas the field-cooled domain state shows irreversible behavior. Hence the lower critical dimensionality dl of the RFIM 2≤dl〈3 in agreement with earlier birefringence experiments. The marked differences between the properties of the d=2 and d=3 RFIM system are elucidated. Our work strongly suggests that all previous neutron studies of similar systems have been incorrectly interpreted as regards dl.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3297-3299 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The d=2 random-field Ising system Rb2Co0.85 Mg0.15F4 has been studied using pulsed, high-field magnetization M measurements. A relatively sharp metastability boundary TF(H) has been discovered which separates a frozen region below from an equilibrium one above TF(H). TF(H) scales as does the (destroyed) phase transition "Tc(H)'' as TN −TF(H) ∝H2/φ, with the measured crossover exponent φ=1.8±0.1 in good agreement with the d=2 susceptibility exponent γ=7/4. As measured in the pulsed field experiment, TF(H) lies well below "Tc(H)'' but above the value of TF(H) obtained from recent neutron scattering studies. The difference in the two values of TF(H) is attributed to the log t time dependence of the approach to equilibrium and to magnetocaloric effects.
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  • 5
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The proportionality between the field-induced shift ΔTc(H) of the transition temperature Tc(H) and the root-mean-square (rms) random-field hRF was studied over a wide range of concentration (0.31≤x≤0.84) in the nearly ideal random-field Ising model (RFIM) system FexZn1−xF2. Tc(H) was determined experimentally from the optical birefringence Δn, for which d(Δn)/dT exhibits a peak proportional to the magnetic specific heat. For all x studied, Tc(H) was found to shift from the H=0 transition at TN as ΔTc(H)ΔTc(H)= cTN h2/φRF as predicted, with φ=1.42±0.03 the universal random exchange to RFIM crossover exponent, after a mean-field correction bH2. The nonuniversal quantity c was found to be of order unity as expected, but slightly x dependent.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3294-3296 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The hysteretic properties of random-field Ising model (RFIM) systems were studied. Using neutron scattering, a relatively narrow metastability boundary TF(H) in the d=2 (d=dl) RFIM system Rb2Co0.85Mg0.15F4 was found to lie well below the rounded specific heat peak "Tc(H)'' of the (destroyed) phase transition. TF(H) scales as TN−TF(H)∝H2/φ with the RF crossover exponent φ=1.74±0.02. At TF(H), equilibrium is approached logarithmically with time. In the d=3 (d〉dl) RFIM system Fe0.6Zn0.4F2 AF order was found to be stable against changes of T and H below the observed sharp phase transition boundary Tc(H), while the field-cooled domain state was not. Capacitance measurements in Fe0.68Zn0.32F2 established that equilibrium prevails for T≥Teq(H) which is slightly above Tc(H). Pronounced logarithmic time dependence is observed at T(approximately-less-than)Tc(H).
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 470 (1986), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 51 (1995), S. 1836-1838 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 58 (1996), S. 6-8 
    ISSN: 1432-0827
    Keywords: Key words: Paget's disease — Resistance — Pamidronate.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Current recommendations for the total dose of intravenous pamidronate to be used in the treatment of Paget's disease range up to 400 mg per course, although up to 980 mg has been suggested for resistant cases. However, in a proportion of Paget's disease patients remission is difficult to induce and maintain. In five patients with resistant symptomatic Paget's disease, in whom a variety of antipagetic therapies had failed to induce remission, we have examined the effects of high dose pamidronate (1.44–2.52 g intravenously over 12–42 weeks). All five subjects had a marked symptomatic improvement, and disease activity was suppressed to a greater extent than had been achieved previously, but in only one did alkaline phosphatase activity suppress into the normal range. A plateau in the biochemical response was evident, with successive pamidronate doses of 120 mg producing smaller decrements in alkaline phosphatase. The plateau was reproducible on repeated courses. Bone biopsies in two patients showed continued pagetic activity with an increased mineralization rate and no osteomalacia. Worthwhile clinical and biochemical improvements can be obtained in patients with resistant Paget's disease by the use of high-dose pamidronate. Though this approach does not seem to cause defective mineralization, it may be difficult to suppress disease activity completely.
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  • 10
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 313 (1985), S. 290-291 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The EXOSAT2 observations of SS Cygni were made on 1984 December 4. SS Cygni was detected in both the medium energy (ME) experiment3 (2-20 keV; 'hard' X rays) and the Channel Multiplier Array (CMA)4 (0.04-2 keV; 'soft' X rays) at flux levels similar to those measured previously in quiescence (ref. ...
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