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  • 1
    Electronic Resource
    Electronic Resource
    Memory effect and temperature behavior in spin valves with and without antiferromagnetic subsystems (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 5692-5695 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Temperature behavior and memory effect in standard spin valves (SV) and SVs with synthetic antiferromagnetic (Co/Ru/Co) (SV-SAF) subsystems have been studied. SV-SAFs show much better temperature stability. Memory effect refers to the phenomenon that the exchange bias can be altered at temperatures (TR's) much lower than the blocking temperature (TB), and these temperatures (TR's) are imprinted into SVs. The memory effect greatly deteriorates the magnetoresistance behaviors in SV. Our results suggest that the memory effect is caused by a distribution of local blocking temperatures (Tb's). The magnetization state in the pinned layer is critical in determining the temperature behavior of HE and magnetoresistance. By partially reversing the magnetization in the pinned ferromagnetic (FM) layers, we are able to separate the temperature dependencies of the local exchange bias (He) associated with regions consisting of different Tb's. Two features have been observed: (1) the local exchange bias (He) with a narrow Tb distribution has a weak temperature dependence; (2) the simple algebraic sum of local He's nearly reproduce the total HE with the difference between these two quantities representing the domain wall energy in the FM layer. On the other hand, SV-SAFs show strong resistance to memory effects because of two factors; the strong exchange coupling through the Ru layer, and the net magnetic moment of Co/Ru/Co layers in SV-SAF being close to zero. The former makes the two SV-SAF FM layers behave coherently, while the latter makes the interaction between the SV-SAF and the external field negligibly small. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371580
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  • 2
    Electronic Resource
    Electronic Resource
    Magneto-impedance effect in soft magnetic tubes (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4807-4809 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Soft magnetic crystalline alloys have been fabricated in a tube form by electrodepositing magnetic FeNi and FeNi–Al2O3 onto W fibers with a diameter of 25 μm. Fine Al2O3 particles have also been incorporated into the magnetic matrix to improve mechanical properties. As-prepared materials are not magnetically soft. With heat treatment, the magnetic properties of these composites are similar to commercial bulk soft FeNi alloys. A giant magnetoimpedance value as large as 190% has been found in as-prepared FeNi-W with a magnetic layer thickness of 20 μm. This value is comparable to GMI observed in amorphous magnetic wires. Experiments also show that GMI values decrease when the Al2O3 content increases in a range from 0 to 7.0 at. %. This behavior is due to the increase in electrical resistivity and magnetic permeability of the samples that modifies the skin effect. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373166
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  • 3
    Electronic Resource
    Electronic Resource
    InAs self-assembled quantum dots grown on an InP (311)B substrate by molecular beam epitaxy (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4186-4188 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Self-assembled InAs quantum dots (QDs) have been grown by solid-source molecular beam epitaxy on a (311)B InP substrate. Transmission electron microscopy clearly shows that a high density of smaller InAs islands can be obtained by using such a high index substrate. After introducing a lattice-matched underlying In0.52Al0.24Ga0.24As layer, the InAs QDs are much more uniform in size and form two-dimensional well ordered arrays. The photoluminescence (PL) spectra also confirm that the InAs QDs grown on underlying In0.52Al0.24Ga0.24As have a better quality than those grown in the In0.52Al0.48As matrix. A simple calculation indicates that the redshift of the PL peak energy mainly results from InAs QDs on underlying In0.52Al0.24Ga0.24As of large size. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1350616
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  • 4
    Electronic Resource
    Electronic Resource
    Memory effect in standard spin valve structures (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4951-4953 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Memory effect has been observed in both standard top and bottom spin valves. The change of the magnetization state in the pinned FM layer, below the blocking temperature, reverses the direction of the exchange bias and destroys the magnetoresistance properties. This reversed exchange bias is much weaker, causing severe consequences in SV applications. This behavior can be explained in terms of blocking temperature distribution in the AFM layer perhaps due to the structural randomness. By varying cooling procedures, the exchange coupling in regions with different blocking temperatures can be separated. It is found that the maximum exchange bias is very close to the sum of the exchange biases in different regions. The domain wall energy in the FM layer has to be taken into account in order to explain the behavior of the reversed bias. The insertion of a synthetic antiferromagnetic subsystem (Co/Ru/Co) stabilizes the magnetization state in the pinned layer because of the additional interlayer coupling through the Ru layer. This suppresses the memory effect. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373212
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  • 5
    Electronic Resource
    Electronic Resource
    New high-Tc cuprate (Tl1−xCrx) (Sr2−yBay)Ca2Cu3O9 (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 3034-3036 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new series of 1223-type (Tl,Cr)-based cuprates, (Tl,Cr)(Sr,Ba)2Ca2Cu3Oz, have been successfully synthesized and identified by powder x-ray diffraction and electron diffraction analyses. Ba partial substitution for Sr promotes the formation of (Tl,Cr)-based 1223-type compounds. Nominal samples, (Tl1−xCrx)-(Sr2−yBay) Ca2Cu3Oz, with 0.15≤x≤0.50 and 0.50≤y≤1.50 are pure or nearly pure 1223 phase and exhibit Tc(ρ=0) in the range of 104–114 K. This new (Tl,Cr)-based high-Tc material may be of importance in practical applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109130
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  • 6
    Electronic Resource
    Electronic Resource
    New 100 K TlSr2(Ca,Cr)Cu2O7 superconducting films (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 3057-3059 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: New TlSr2(Ca,Cr)Cu2O7 superconducting films on MgO(100) substrates have been prepared and characterized. The superconducting films were fabricated via a two-step process. Precursor SrCaCrCuO films were first deposited by spray pyrolysis at temperature of 350–400 °C, and thallium was then incorporated by heating the precursor films between unfired TlSrCaCrCuO bulk pellets at 880–900 °C in an oxygen atmosphere. The films were then cooled down to room temperature in an oxygen or argon atmosphere. The superconducting films were single 1212 phase with c-axis perpendicular to the surface of the MgO(100) substrates. Onset temperatures up to 110 K and zero-resistance temperatures up to 100 K were achieved. The critical transport currents (Jc) of the films were about 7×103 A/cm2 at 77 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106755
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  • 7
    Electronic Resource
    Electronic Resource
    K6[As6V15O42(H2O)].6H2O (1998)
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 1556-1558 
    Details
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108270198005629
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  • 8
    Electronic Resource
    Electronic Resource
    Crystallization and preliminary X-ray analysis of Citrobacter amalonaticus methylaspartate ammonia lyase (2001)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 57 (2001), S. 1922-1924 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Methylaspartate ammonia lyase (MAL) catalyses the reversible α,β-elimination of ammonia from L-threo-(2S,3S)-3-methylaspartic acid to give mesaconic acid. Crystals of Citrobacter amalonaticus MAL have been obtained by the hanging-drop method of vapour diffusion using ammonium sulfate as the precipitant. Three crystal forms were obtained from identical crystallization conditions, two of which (forms A and B) diffract to high resolution, whilst the third form diffracted poorly. Crystals of form A diffract to beyond 2.1 Å and have been characterized as belonging to one of the enantiomorphic space groups P4122 or P4322, with unit-cell parameters a = b = 66.0, c = 233.1 Å, α = β = γ = 90° and a monomer in the asymmetric unit. Crystals of form B diffract to beyond 1.5 Å and belong to space group C222, with unit-cell parameters a = 128.3, b = 237.4, c = 65.8 Å, α = β = γ = 90° and a dimer in the asymmetric unit. Determination of the structure of MAL will be an important step in resolving current conflicts concerning the enzyme mechanism which differ between one which places MAL as a member of the superfamily of ammonia lyases whose catalytic activity requires a cofactor formed by post-translational modification of the enzyme and another which links MAL to the enolase superfamily.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444901016675
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  • 9
    Electronic Resource
    Electronic Resource
    Enzymes in organic chemistry, part 1: Enantioselective hydrolysis of α-(acyloxy)phosphonates by esterolytic enzymes
    Amsterdam : Elsevier
    Tetrahedron: Asymmetry 4 (1993), S. 109-120 
    Details
    ISSN: 0957-4166
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/S0957-4166(00)86021-8
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis and superconductivity of a new 1222-type T1-based layered cuprate (T1, Nb) Sr2(Nd, Ce)2Cu2O z (1993)
    Springer
    The European physical journal 90 (1993), S. 19-22 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Synthesis and superconductivity of a new 1222-type layered cuprate (Tl1−x Nb x ) Sr2(Nd1−y Ce y )2Cu2O z have been studied. The structure of this cuprate is directly related to that of Nb-1222 NbSr2(Nd, Ce)2Cu2O z with tetragonal body-center lattice. Partial substitution of Tl for Nb in Nb-1222 phase improves its superconductivity. (Tl1−x Nb x ) Sr2(Nd0.75Ce0.25)2Cu2O z samples prepared by the typical procedure exhibit superconductivity withT c of 30–40 K. Effects of Tl and Nb on superconductivity of this cuprate are briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01321028
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