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  • 1
    Electronic Resource
    Electronic Resource
    Solvent influence on the magnetic field effect of polymethylene-linked photogenerated radical ion pairs (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4098-4105 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The solvent viscosity and polarity dependence of the magnetic field effect in polymethylene-linked radical ion pairs, which were generated by photoinduced intramolecular electron transfer in compounds of the type pyrene–(CH2)n–N,N-dimethylaniline, has been studied. A stochastic Liouville equation is used, in which the dynamics of the polymethylene chain, the spin Hamiltonian as a function of the varying radical distance (exchange interaction), and a distance-dependent back electron transfer rate are incorporated. The results are compared with predictions made on the basis of the (static) subensemble approximation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457624
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  • 2
    Electronic Resource
    Electronic Resource
    JET soft x-ray diode array diagnostic (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 2142-2144 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The arrays of silicon diodes recently installed on the Joint European Torus (JET) measure the plasma soft x-ray emission with high temporal and spatial resolution, allowing magnetohydrodynamic (MHD) effects to be investigated. The diagnostic consists of two "pinhole'' cameras which view the same poloidal cross section in orthogonal directions. A data-acquisition system based upon three cascaded digital filters can convert the 200-kHz detector signal analog-to-digital converter (ADC) output to lower sampling rates of 10, 1, and 0.1 kHz. Initially, studies have concentrated on the sawtooth collapse. By means of a trigger system data on the sawtooth crash have regularly been recorded at a sampling frequency of 200 kHz. Using tomographic reconstruction techniques, the soft x-ray emissivity cross section during the crash has been reconstructed. First results during ion cyclotron radio frequency (ICRF) heating show no precursor activity prior to the sawtooth collapse, while during the crash, the hot central plasma is displaced off axis by about 30 cm on a time scale of 50–200 μs, after which a hollow soft x-ray profile forms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139200
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  • 3
    Electronic Resource
    Electronic Resource
    JET x-ray pulse-height analysis system (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 693-699 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The pulse-height-analysis (PHA) system installed on the Joint European Torus (JET) measures the plasma soft x-ray emission (2–30 keV) with an energy resolution of 450 eV and a time resolution of 200 ms. This diagnostic includes three Si(Li) detectors, equipped with sets of remotely controlled apertures and filters, which view the plasma in the midhorizontal plane of the torus along a single tangential line of sight. Automatic analysis of the spectra yields the central electron temperature, the central concentrations of chlorine, chromium, and nickel, and Zeff. Simulations of the measured spectra using a radiation code provides the basis to construct a consistent picture of the soft x-ray emission in the central region of JET plasmas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139812
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  • 4
    Electronic Resource
    Electronic Resource
    Spin-polarized photoemission study of epitaxial Gd(0001) films on W(110) : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6769-6771 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Surface magnetic properties of epitaxial Gd(0001) films grown on W(110) were studied with spin-polarized resonant 4f photoemission. Films grown at room temperature and subsequently annealed to 550 °C show 66% polarization at 150 K, whereas films grown at 400 °C show only 46% polarization. Both types of films exhibit surface enhanced magnetic order, with the highest observed surface critical temperature exceeding the bulk value by as much as 60 K. For the first time, a rich variety of novel surface magnetic phenomena, i.e., sizeable perpendicular polarization component and unusual temperature hysteresis in the spin polarization, are observed, demonstrating that surface magnetic reconstruction is present in Gd(0001) films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352480
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  • 5
    Electronic Resource
    Electronic Resource
    Coercivity mechanism in CoPt alloy films with perpendicular magnetic anisotropy (abstract) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4922-4922 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The coercivity is one of the key parameters for defining a suitable magneto-optic recording material. In order to get insight into coercivity mechanisms we have studied the magnetization reversal processes by means of magneto-optic methods in CoPt alloy films. These films were prepared in UHV by coevaporation with a typical composition ratio of Co28Pt72 and show excellent perpendicular magnetic anisotropy at elevated substrate temperatures during deposition. STM and x-ray measurements reveal characteristic grain size of about 15–20 nm and dispersion of crystallite axis of the order of 0.5°, respectively, which varies only slightly with total film thicknesses of 5–50 nm. The magnetization reversal processes are investigated by using polar Kerr microscopy and were found to be dominated by domain formation and domain wall propagation. A micromagnetic model was developed which describes the film as an ensemble of single domain particles. The size of these single domain particles was chosen to be of the order of the average grain size. In the numerical simulation we include dipolar interaction and domain wall energy contribution. The comparison of the results of the simulation with the experimental results clearly points out that the microstructure is responsible for the magnetization reversal behavior. A thermal as well as thermally activated magnetization processes contribute to the reversal mechanism. The coercivity is predominantly determined by pinning on grain boundaries. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361588
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  • 6
    Electronic Resource
    Electronic Resource
    Magneto-optical investigation of the fcc–bcc phase transition of Fe wedges sandwiched between CuNi alloys (abstract) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4990-4990 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a systematic investigation of the fcc–bcc structural phase transition of thin Fe films sandwiched between CuNi alloys. The structures were of the type substrate/20 nm Pt/10 nm CuNi/0–2 nm Fe wedge/1 nm CuNi/2 nm Pt. All films were deposited in high vacuum by electron beam evaporation at temperatures ranging from 400 °C (Pt seed layer) to 100 °C (CuNi alloy layers and Fe wedge) to 20 °C (Pt cap layer). The CuNi composition ratio was varied in 10 at. % steps in order to vary its lattice constant from a=0.3607 nm (Cu) to 0.3517 (Ni) nm, which encompasses the value of gamma Fe (fcc low spin state). X-ray diffraction measurements reveal strong (111) texturing with an alignment of the Pt 〈111〉 axis better than 5 deg (rocking curve width) of the completed structures. Kerr loops in fields ±18 kOe were recorded as function of the Fe-wedge position with a spatial resolution of about 0.8 mm, corresponding to 0.1 nm Fe thickness resolution. These hysteresis loops reveal the saturation Kerr angle (0.1 mdeg resolution), the saturation field (anisotropy field) and a paramagnetic slope, which are all analyzed as function of the Fe thickness and the CuNi composition. Clear evidence for the formation of paramagnetic Fe is found for Cu-rich CuNi alloys, where a Kerr rotation below the resolution limit of our apparatus extends up to (approximately-greater-than)2 nm Fe thickness. The transition thickness from fcc to bcc Fe, as characterized by the onset of a linear uptake of the Kerr rotation, shows a pronounced maximum near about 25 at. % Ni, indicating that a small compression of the Fe lattice constant (about −2%) leads to the nonferromagnetic fcc Fe state. A similar study, using CuAu alloys with the aim of characterizing the high spin ferromagnetic fcc Fe phase, is in progress. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361613
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  • 7
    Electronic Resource
    Electronic Resource
    Interface analysis of (110)-oriented Co/Pt superlattices with large magnetic anisotropies using x-ray diffraction (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 908-913 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on studies of the profiles of the strain field components in epitaxially grown (110)-oriented Co/Pt superlattices with fixed Pt layer thickness (nominally 18 A(ring)) and varying Co layer thickness. The strain profiles in the growth direction as well as fluctuations in lattice parameters at the interfaces are obtained using a parameter refinement method for the quantitative analysis of high angle aitch-theta–2aitch-theta x-ray diffraction scans. We find that all strain components originate only from the Co-Pt interfaces. Off-axial x-ray scattering measurements provide for the in-plane strain components, which are found to increase with increasing Co layer thickness. From the obtained strain fields the in-plane uniaxial magnetic anisotropy contributions caused by magnetoelastic interactions are calculated, which agree well with experimentally observed values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357768
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of submonolayer coverage on magnetic anisotropy of ultrathin cobalt films M/Co/Au(111) with M=Au, Cu, Pd : The 6th joint magnetism and magnetic materials (MMM)-intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6078-6080 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using in situ polar magneto-optical Kerr-effect measurements, the variation of the Kerr rotation and magnetic anisotropy of a (0001)Co ultrathin film on a (111)Au substrate has been precisely recorded, during the first stages of the growth of an overlayer of metal M=Au, Cu, and Pd. As reported earlier, a drastic increase of the magnetic anisotropy was observed, with a peak around 1 monolayer of overlayer thickness. From a careful study of the variation of the remanent Kerr rotation, it could be shown that only the interface contribution to the anisotropy changes with the overlayer thickness, while the bulk contribution remains mostly constant. The overall behavior can be interpreted in terms of electronic effects in the metal overlayer, acting on the interface anisotropy via band hybridization at the interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358370
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  • 9
    Electronic Resource
    Electronic Resource
    Magnetic reversal in perpendicularly oriented thin films subjected to picosecond magnetic fields (abstract) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6488-6488 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic reversal mechanism in perpendicularly oriented, premagnetized Co based thin film alloys, induced by ultra short magnetic field exposure of a few picoseconds duration has been studied. Field pulses with a magnitude of several thousand Tesla were generated by the 50 GeV final focus electron beam at the Stanford Linear Accelerator Center (SLAC). Characteristic remanent domain patterns are observed in these films long after field exposure using polar Kerr microscopy. Complete reversal of the magnetization is found to occur during a single spin precession event of 6.0 ps duration where the inplane-field amplitude is greater or equal to the macroscopically determined perpendicular anisotropy field. Further, a wide transition range, dividing the reversed and nonreversed regions is observed which is broken into a quasi periodic stripe domain structure with stripe-width 0.3 μm. As a main result of this experimental study we find that magnetization reversal on this time scale is solely governed by the intrinsic effective field, i.e., anisotropy- and demagnetization-field contributions, rather then by complex curling and buckling mechanisms. Unique insight into fundamental spin reversal mechanisms and their ultimate speed in thin magnetic recording films is provided by these experiments. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362451
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  • 10
    Electronic Resource
    Electronic Resource
    X-ray magnetic circular dichroism studies of multilayered thin films of 3d transition metals (invited) (abstract) : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 5807-5807 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray magnetic circular dichroism (XMCD) is used to probe both the spin and orbital d moments of Co in Co/Pd, Co/Pt, and Co/Ni multilayers, and in a Au/Co-wedge/Pd structure. While the spin moment per Co atom is found to be constant within the experimental error, the orbital moment shows a strong dependence both on the chemical environment and on the thickness of the Co layer. In particular, we find an orbital moment enhancement of up to a factor of three for a Co layer thickness of four atomic layers in the present Au/Co/Pd sandwich structure. This enhancement decays to the bulk Co value, roughly following a 1/dCo dependence, thus confirming its interfacial origin. The relevance of these observations with respect to the perpendicular magnetic anisotropy in these samples will be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355571
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