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  • 1
    Electronic Resource
    Electronic Resource
    Spin-polarized electron transport in ferromagnet/semiconductor hybrid structures (invited) (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6740-6744 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two major problems in spin electronics remain to be solved: room temperature spin injection at a source and spin detection at a drain electrode. The lateral size of magnetic contacts and the presence of a potential barrier at the interface are believed to have a key influence on the efficiency of both of these processes. We therefore aimed to clarify these issues by studying spin-polarized transport across epitaxially grown single crystal Fe (001)/GaAs nanoclusters and at the Schottky barrier formed at Ni80Fe20/GaAs interfaces. We observed a negative contribution to the magnetoresistance of an ultrathin (2.5 ML) discontinuous epitaxial Fe film as occurs in tunnel magnetoresistance. This result suggests that spin transport via GaAs is possible on the nanoscale. In the continuous NiFe/GaAs structures, circularly polarized light was used to create a population of spin-polarized electrons in the GaAs substrate and spin-polarized electron transport across the interface at room temperature was detected as an electrical response associated with the field-dependent photocurrent. Surprisingly, highly efficient spin transmission is observed at room temperature, indicating that there is no significant loss of spin polarization for electrons crossing the interface. This result unambiguously demonstrates that spin detection is possible at room temperature in a continuous ferromagnet/semiconductor contact in the presence of the Schottky barrier. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1361045
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  • 2
    Electronic Resource
    Electronic Resource
    Domain wall trapping in controlled submicron ferromagnetic elements (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4727-4729 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The domain configuration in permalloy wires (30 nm thick, 10 μm wide, and 205 μm long) with a wide size range of a narrow central bridge (5 μm long and w μm wide; 0.5≤w≤10 μm) were investigated in both their demagnetized and remanent states using magnetic force microscopy and the results were confirmed by micromagnetic calculations. At the bridge region, domain walls were found to be shifted by a small external field. Scanning magneto-optical Kerr effect revealed that the coercivity in these structures are the same as that in a straight wire, suggesting that domain wall movement is the dominant process in the magnetization reversal of these structures. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373140
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  • 3
    Electronic Resource
    Electronic Resource
    Domain wall trapping probed by magnetoresistance and magnetic force microscopy in submicron ferromagnetic wire structures (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 6178-6180 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetoresistance (MR) and domain structure of submicron NiFe wires and crosses fabricated using advanced electron beam lithography techniques have been studied in order to investigate the dependence of MR on the detailed domain configurations. While the 0.5 μm wire shows almost no longitudinal MR, the cross sample clearly shows a variation of the resistance upon sweeping the magnetic field, indicating an MR effect associated with the domain structures which form at the junction. By correlating the MR curves with the domain configurations obtained from magnetic force microscopy, we found that a 180° domain wall trapped in the junction of this 0.5 μm cross contributes a negative MR effect. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370213
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  • 4
    Electronic Resource
    Electronic Resource
    Spin-dependent electron transport at the ferromagnet/semiconductor interface (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5804-5806 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A search for spin-dependent electron transport at the ferromagnet/semiconductor interface has been made by measuring the bias dependence of a photon excited current through the interface. A circularly polarized laser beam was used to excite electrons with a spin polarization perpendicular to the film plane. In samples of the form 3 nm Au/5 nm Ni80Fe20/GaAs (110), a significant transport current was detected with a magnitude dependent on the relative orientation of the spin polarization and the magnetization vector. At perpendicular saturation, the bias dependence of the photocurrent is observed to change in the range 0.7–0.8 eV when the helicity is reversed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369925
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  • 5
    Electronic Resource
    Electronic Resource
    Spin-dependent electron transport in NiFe/GaAs Schottky barrier structures (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4670-4672 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoexcitation at the Schottky barrier formed between 5 nm thick Ni80Fe20 films and both n+- and p−-type GaAs(100) substrates with doping density in the range 1023≤n(p)≤1025 m−3 was investigated using circularly polarized laser light. A helicity-dependent photocurrent dependent upon the magnetization configuration of the film and the Schottky barrier height was detected. The results provide evidence of spin-dependent electron transport through the NiFe/GaAs interface and show that the Schottky barrier height controls the spin-dependent current passing from the semiconductor to the ferromagnet. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373125
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  • 6
    Electronic Resource
    Electronic Resource
    Micromagnetism in mesoscopic epitaxial Fe dot arrays (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 7019-7021 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The domain structures of epitaxial Fe (20 nm)/GaAs(100) circular dot arrays (diameters from 50 to 1 μm) were studied with magnetic force microscopy. A transition from a single domain to a multidomain remanent state was observed upon reducing the dot diameter beneath 10 μm in dot arrays with the separation twice the dot diameter. When the separation is reduced to half the dot diameter, the single domain states were found to "collapse" into stripe-like multidomain states due to local dipole coupling between dots. Micromagnetic simulations further suggest that for ultrathin Fe dots of less than about 2 nm thickness the diameter does not have a significant influence on the domain structures due to a dramatic reduction of the dipole energy. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372917
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  • 7
    Electronic Resource
    Electronic Resource
    Domain nucleation processes in mesoscopic Ni80Fe20 wire junctions (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 3032-3036 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetization reversal process in permalloy (Ni80Fe20) wire junction structures has been investigated using magnetoresistance (MR) measurements and scanning Kerr microscopy. A combination of electron beam lithography and a lift-off process has been utilized to fabricate wires consisting of two 200 μm length regions with distinct widths w1 and w2 in the range 1–5 μm. Longitudinal MR measurements and magneto-optic Kerr effect hysteresis loops demonstrate that the magnetization reversal of the complete structure is predominantly determined by the wider region for fields applied parallel to the wire axis. Magnetic force microscopy and micromagnetic calculations show that several domain walls nucleate in the wider part and are trapped in the junction area. This implies that domain nucleation at the junction of the wire initiates magnetization reversal in the narrow half. As a consequence, the switching fields are found to be identical in both halves in this case. These results suggest the possibility of designing structures which can be used to "launch" reverse domains in narrow wires within a controlled field range. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372295
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  • 8
    Electronic Resource
    Electronic Resource
    Magnetic nanoscale dots on colloid crystal surfaces (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 748-750 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate that uniform, ordered, single-domain magnetic nanoscale dots can be fabricated on concentrated colloid surfaces. The substrate consists of compact silica nanosphere arrays grown on a glass wafer. Through the subsequent deposition and oxidation treatment of a Co film, monodisperse magnetic Co nanoscale dot arrays with controlled magnetic properties and size were obtained. We suggest that magnetic dots deposited on colloidal surfaces might open a way of developing artificially nanostructured materials for fundamental studies in nanomagnetism and for applications such as patterned magnetic recording media. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125882
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