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  • 1
    Electronic Resource
    Electronic Resource
    The influence of impurities within the barrier on tunneling magnetoresistance (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5801-5803 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Tunneling magnetoresistance (TMR) of a ferromagnetic tunnel junction is calculated in the presence of nonmagnetic metal impurities and disorder in the barrier layer within a single-band tight-binding model. We found that the introduction of impurities which have onsite atomic energies close to the Fermi level leads to a rapid drop in TMR as a function of the impurity concentration. This results from the increasing number of localized electronic levels close to the Fermi energy which promote the formation of highly conducting channels within the insulator. With increasing atomic energy of the impurities, tunneling via the impurity band results in higher values of TMR due to a higher effective potential barrier associated with this mechanism of tunneling. In this case introduction of impurities within the barrier can provide enhanced values of conductance without a significant reduction in TMR, which is required for MRAM applications of tunnel junctions. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369924
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  • 2
    Electronic Resource
    Electronic Resource
    Oxygen-induced positive spin polarization from Fe into the vacuum barrier (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 5230-5232 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Bonding at the ferromagnet–insulator interface is an important factor which influences spin polarization of the tunneling current in ferromagnetic tunnel junctions. In this article we investigate the spin-polarized electronic structure of the (001) surface of body-centered-cubic iron covered by an oxygen overlayer, as this could reflect the mechanism of bonding and spin polarization in iron/oxide tunnel junctions. The Fe/O atomic structure is optimized using the plane-wave code CASTEP within the spin-polarized generalized-gradient approximation. The electronic structure and local densities of states are calculated using the linear muffin-tin orbital method. The results show hybridization of the iron 3d orbitals with the oxygen 2p orbitals, the strong exchange splitting of the former resulting in exchange-split bonding and antibonding oxygen states. These antibonding states are partially occupied for the majority spins but are almost unoccupied for the minority spins, which leads to a positive spin polarization in the density of states of the oxygen atoms at the Fermi energy. This positive spin polarization propagates from oxygen into the vacuum barrier. This is opposite to what is observed for clean Fe films, where the surface Fe layer has a negative spin polarization at the Fermi energy and remains negative into the vacuum. We infer that this p–d bonding mechanism might be responsible for the experimentally observed positive spin polarization of the tunneling current from ferromagnetic metals through alumina. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373304
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  • 3
    Electronic Resource
    Electronic Resource
    Importance of spin-independent scattering potentials in giant magnetoresistance : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4579-4581 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate that the giant magnetoresistance (GMR) effect in magnetic multilayers can be explained quantitatively in terms of the scattering of electrons from a spin-independent random potential that arises from the grown-in defects within the multilayer. We have calculated the GMR ratio for Co4/Cu4 and Fe4/Cr4 (001) multilayered systems within the Kubo–Greenwood formalism assuming that the on-site atomic energies are disordered randomly within a realistic spd tight-binding model. Our predictions are in good agreement with experiment and demonstrate that (i) increasing disorder causes a drop of GMR in multilayers, (ii) GMR for the current perpendicular to the plane is typically by a factor of two higher than GMR for the current in the plane, and (iii) the semiclassical treatment of conductivity applied to magnetic multilayers results in overestimated values of GMR due to the neglect of interband transitions. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365434
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  • 4
    Electronic Resource
    Electronic Resource
    Electronified (1989)
    [s.l.] : Nature Publishing Group
    Nature 338 (1989), S. 551-551 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] THE classic textbooks by Hume-Rothery and Raynor on the electron theory of metals were published soon after the end of the Second World War. They were imbued with the optimism, prevalent at that time amongst scientists, that science could win the peace just as it had helped win the war. In response ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/338551a0
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  • 5
    Electronic Resource
    Electronic Resource
    Bond-order potentials: Can they bridge the electronic-atomistic length-scale gap? (1996)
    Springer
    Journal of computer-aided materials design 3 (1996), S. 149-156 
    Details
    ISSN: 1573-4900
    Keywords: Bond-order potentials ; Atomistic simulations ; Giant magnetoresistance ; Diamond-like carbon ; Materials modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Materials modelling involves research over a broad range of hierarchies from the electronic at the Ångström length scale, through the atomistic and microstructural, to the continuum at the meter length scale. In this paper the theory of giant magnetoresistance and the simulation of the growth of diamond-like carbon are given as illustrative examples of modelling at the electronic and atomistic length scales, respectively. The question is then addressed as to whether the gap between the electronic and atomistic hierarchies can be bridged by the novel many-atom bond-order potentials that may be derived as an exact description of the covalent bond within the tight-binding approximation to the electronic structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01185647
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