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  • 1995-1999  (27)
  • 1990-1994  (31)
  • 1985-1989  (17)
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  • 1
    Electronic Resource
    Electronic Resource
    Neutron scattering investigation of the ordered state of the nuclear spins in Cu at 60 nK (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5433-5435 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the magnetic structure of the nuclear spin system in Cu below 60 nK by means of neutron scattering. The observation of the nuclear (100) superlattice reflection proves the theoretically predicted antiferromagnetic arrangement of the nuclear spins. The critical field at the lowest temperatures was 0.24 mT. Around 0.1 mT the (100) reflection could not be observed. This is taken as an indication for, possibly, a reorientation phase transitition at this field. Therefore, the phase diagram contains at least two phases. For 0.1 mT〈B〈0.24 mT strong time dependencies of the ordering were observed. At low fields (B〈0.1 mT) nucleation times of the order of 10 s have been observed. These results are discussed with respect to the cooling technique: Adiabatic demagnetization requires constant entropy, a rather unusual way to bring a system from the paramagnetic to the ordered phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344580
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  • 2
    Electronic Resource
    Electronic Resource
    Neutron scattering studies of the spin dynamics in nonlinear and Haldane systems (invited) (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5593-5598 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In 1D magnets contributions to the spin dynamics which are outside the scope of spin-wave theory can be studied theoretically as well as experimentally. Two prominent examples of such effects are discussed here: solitons and the Haldane gap. We discuss inelastic polarized neutron scattering results on the stability of solitons in CsNiF3 and on the existence of the Haldane gap in CsNiCl3. In both cases, the separate determination of the different correlation functions 〈SαSα〉 with α=x,y,z is essential for definite conclusions: Solitons in CsNiF3 appear to be much more stable than expected from classical theories, and the Haldane gap is the only explanation for the observed gaps in CsNiCl3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345895
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  • 3
    Electronic Resource
    Electronic Resource
    Fast thermoremanent magnetization in the insulating spin glass CsNiFeF6 : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5466-5467 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: With a newly built superconducting quantum interference device magnetometer, the time range of measurements of the thermoremanent magnetization (TRM) was extended to less than 10 ms. This new method allows a direct investigation of aging and relaxation in the spin glass region for short times. As a first example for fast TRM, the magnetization in a single crystal of the insulating spin glass CsNiFeF6 was measured in the time range −2〈log(t/s)〈3 at magnetic fields between 2 and 20 G at temperatures between 4.7 and 1.7 K. Additionally, the zero field and field cooled magnetization of this sample to temperatures up to 9 K was studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353667
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  • 4
    Electronic Resource
    Electronic Resource
    Neutron diffraction determination of the nuclear spin ordering in Cu and Ag at nano- and subnano-K temperatures (invited) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5078-5080 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spontaneous nuclear spin ordering in the simple diamagnetic metals Cu and Ag has been studied by neutron diffraction using the spin dependent part of the nuclear cross section. Simple antiferromagnetic ordering of type I has been found in zero field for these fcc-systems below 60 and 560 pK for Cu and Ag, respectively. The ordering in an applied field has been investigated and the phase diagrams have been determined: a very complex phase diagram with different magnetic structures, strong hysteresis, and time dependence was found for Cu, while in Ag the phase diagram is very simple. Comparison with ab initio calculations allows a rather deep insight into the interactions leading to the ordering. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361579
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  • 5
    Electronic Resource
    Electronic Resource
    Optical transitions in (ZnCo)Se and (ZnFe)Se: Role of an effective p–d exchange (invited) : 38th Annual Confrerence on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 5719-5724 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper we discuss photoluminescence (PL) and Raman excitations in the diluted magnetic semiconductors Zn1−xCoxSe and Zn1−xFexSe. The PL spectra associated with isolated crystal field d levels are found to rapidly weaken and/or broaden as the transition metal ion concentration approaches and increases beyond a critical value. In addition a Raman continuum, that overlaps with the optical phonon, is observed to develop when the PL features are modified. In the corresponding Zn1−xCoxSe samples the optical phonons acquire a characteristic Fano line shape suggestive of its coupling to the Raman continuum. It is proposed that these changes to the optical transitions arise from the enhancement of an effective p–d hybridization between low-lying d levels and band electrons with increasing x—an effect largely due to the proximity of the Co2+ and Fe2+ crystal field ground levels to the valence band maximum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355594
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  • 6
    Electronic Resource
    Electronic Resource
    Meyer–Neldel behavior of deep level parameters in heterojunctions to Cu(In,Ga)(S,Se)2 (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 2888-2890 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Admittance spectroscopy was measured on Cu(In,Ga)(S,Se)2 thin film and single crystal heterojunctions. The emission rates of defects for various near-stoichiometric compositions follow a Meyer–Neldel rule, showing increasing attempt-to-escape frequencies with increasing defect depth. Defects in highly (In,Ga)-rich material showed lower attempt-to-escape frequencies and follow a separate Meyer–Neldel relation. Repetitive air annealing of a CuInSe2 heterojunction revealed a shift of the depth and capture cross section of an observed defect. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117352
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  • 7
    Electronic Resource
    Electronic Resource
    n-ZnO/p-CdSiAs2 heterojunction solar cells (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 1560-1561 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Heterojunction solar cells were prepared by magnetron sputtering of n-ZnO onto p-CdSiAs2 single crystals. These crystals were grown by chemical vapor-phase transport and have a resistivity of 2 Ω cm, a Hall mobility of 300 cm2/V s, and a net carrier density of 1016 cm−3 at room temperature. The heterojunctions exhibit short-circuit current densities up to 12 mA/cm2 and open-circuit voltages between 180 and 250 mV with power conversion efficiencies up to 1% under 72 mW/cm2 halogen lamp illumination. Open-circuit voltage values could be increased by heat treatment at 80 °C for 15 min in an argon atmosphere. By measuring the reflection and the quantum yield versus wavelength the efficiency losses in the short-wavelength region could be attributed to the corresponding high reflection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341835
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  • 8
    Electronic Resource
    Electronic Resource
    Inelastic neutron scattering studies on 1D near-Heisenberg antiferromagnets: A test of the Haldane conjecture (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3953-3955 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Our studies of the spin dynamics for two near-Heisenberg antiferromagnets (AFMs) revealed: In CsNiCl3 (S=1) at low T(very-much-less-than)TN we confirm the conclusions given earlier, but disagreement with the spin-wave calculations used is found for the eigenvectors. For T〉TN, the most important result is the observation that all 〈SαSα〉 (α=x,y,z) are identical, demanding another interpretation for the gap observed than the easy axis one. In CsVCl3 (S= (3)/(2) ) we could not observe any inconsistency in the microscopic parameters determined above and below TN. Although there is a striking coincidence with Haldane's conjecture [unexplained gap for S=1 (CsNiCl3), no such gap for S= (3)/(2) (CsVCl3)], it is not clear whether this can be considered a proof for Haldane's conjecture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338595
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  • 9
    Electronic Resource
    Electronic Resource
    Influence of linear and nonlinear excitations in the ferromagnetic S=1/2 chain system [C6H11NH3]CuBr3 (CHAB) (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3956-3958 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic properties of the title compound have been studied by measurements of the nuclear spin-lattice relaxation time T1, the uniform magnetization M, and by quasielastic and inelastic neutron scattering. The field and temperature dependence of T1 and the wave-number dependence of the magnon excitation energy can be satisfactorily described by linear spin-wave theory. A good description of M, however, requires a contribution from kink solitons. The available evidence suggests that, in contrast to the linear excitations, the nonlinear excitations in CHAB for B(parallel)c can be described very well by a classical model, which is consistent with the interpretation of earlier heat-capacity measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338596
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  • 10
    Electronic Resource
    Electronic Resource
    Thin-film CdSe: Photoluminescence and electronic measurements (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 2601-2606 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electronic properties of thin CdSe films prepared through physical vapor transport were investigated using photoluminescence (PL) and electronic measurements. The films were studied at each of the main preparation steps, i.e., evaporation, annealing, etching, and finally photoetching. At 3 K two distinct donor-acceptor (DA) transitions at 1.75 and 1.70 eV were found in the photoluminescence spectra in addition to deep states at about 1.55 eV at 20 K. These DA transitions which are produced mainly during the evaporation might be associated with group VII and with alkali metal impurities. After each preparation step the DA transitions change their intensities. It is shown that photoetching of the films leads to a removal of the deep centers, while the 1.75 eV transition is blue shifted. In contrast with single-crystal CdSe the intensity of the PL increases after photoetching. The results of the PL are consistent with the electronic measurements. They are explained in terms of a previously published model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341649
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