Search Results - (Author, Cooperation:Y. B. Xu)

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  1. 1
    Y. L. Tang ; Y. L. Zhu ; X. L. Ma ; A. Y. Borisevich ; A. N. Morozovska ; E. A. Eliseev ; W. Y. Wang ; Y. J. Wang ; Y. B. Xu ; Z. D. Zhang ; S. J. Pennycook
    American Association for the Advancement of Science (AAAS)
    Published 2015
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    Publication Date:
    2015-04-18
    Publisher:
    American Association for the Advancement of Science (AAAS)
    Print ISSN:
    0036-8075
    Electronic ISSN:
    1095-9203
    Topics:
    Biology
    Chemistry and Pharmacology
    Computer Science
    Medicine
    Natural Sciences in General
    Physics
    Published by:
    Latest Papers from Table of Contents or Articles in Press
  2. 2
    Xu, Y. B. ; Jin, Q. Y. ; Zhai, Y. ; Lu, M. ; Miao, Y. Z. ; Bie, Q. S. ; Zhai, H. R.

    [S.l.] : American Institute of Physics (AIP)
    Published 1993
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    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The complex magneto-optical Kerr rotation spectra of Fe/Cu and FeCo/Cu bilayers and compositionally modulated films (CMF) were studied experimentally and theoretically. In the bilayers, an enhancement of Kerr ellipticity εk by a factor of 5 was observed at long wavelength side, while the Kerr rotation θk can only be enhanced by a factor of 2 around the plasma edge of Cu. In the CMFs, εk was enhanced by 60% but no θk enhancement was observed. Theoretical analyses showed that both the magnitude of effective ε˜xye and the magnitude and signs of effective Ae and Be are important for magneto-optical enhancement.
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    Articles: DFG German National Licenses
  3. 3
    Zhai, H. R. ; Xu, Y. B. ; Lu, M. ; Miao, Y. Z. ; Hogue, K. L. ; Naik, H. M. ; Ahmad, M. ; Dunifer, G. L.

    [S.l.] : American Institute of Physics (AIP)
    Published 1991
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    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Different thickness dependencies of the magneto-optical Kerr effect of the magnetic (Co, Ni, and Fe)/nonmagnetic (air, glass, Cu, and W) bilayer structures were studied experimentally and theoretically, showing the complicated influence of the dielectric constants of the underlying substrate.
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    Articles: DFG German National Licenses
  4. 4
    Zhou, S. M. ; Lu, M. ; Zhai, H. R. ; Miao, Y. Z. ; Tian, P. B. ; Wang, H. ; Xu, Y. B. ; Huang, H. B.

    [S.l.] : American Institute of Physics (AIP)
    Published 1991
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    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Bilayers Nd-Fe/Cu and Nd-Fe/Al made by vacuum evaporation were studied. The magneto-optical Kerr effect (MOKE) and reflectivity spectra were measured. For Nd-Fe/Cu with low Nd content and small thickness of Nd-Fe layer there is a peak in the MOKE spectrum and a broad MOKE enhancement. The position is located near the plasma edge of Cu. When the content of Nd exceeds 37 at. %, there is no Kerr peak in the MOKE spectrum of Nd-Fe/Cu. When the thickness of the magnetic layer is larger but still less than the light penetration depth, the position of the peak moves towards the long-wavelength side. For Nd-Fe/Al there is a broad enhancement in the short-wavelength region, but no Kerr peak occurs no matter how the magnetic layer changes. The results presented show that the necessary conditions for MOKE enhancement in bilayers are suitable values of n and k of the reflector, whether the reflector has a plasma edge or not, and the enhancement also depends on the properties of the magnetic layer.
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  5. 5
    Xu, Y. B. ; Ha, K. F. ; Wang, Z. G. ; Wang, X. H. ; Li, J.

    [S.l.] : American Institute of Physics (AIP)
    Published 1991
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    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Dislocation distribution near the crack tip of I and II modes in bulk aluminum single crystal has been decorated by using the etching pit technique and then was observed by scanning electron microscopy. It has been shown that two kinds of distribution of dislocations, i.e., shielding and antishielding dislocations are found to exist near the crack tip. In addition to these, the dislocation-free zone is still observed to be between the crack tip and the plastic zone. According to Rice and Thomson [Philos. Mag. 29, 73 (1974)], the dislocation mode of the elastic-plastic crack is extended to include the antishielding dislocations as part of a crack-tip equilibrium configuration, which may be described as follows: (μb/2π) (∫−e−a+∫−c−s +∫sc+∫ae)[ f(x')/(x−x')]dx'+σa=0, when ||x||〈C, or σf, when c〈||x||〈s and e〈||x||〈a. The factors affecting the dislocation distribution are discussed in detail.
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  6. 6
    Zhai, H. R. ; Zhou, S. M. ; Lu, M. ; Miao, Y. Z. ; Tian, P. B. ; Wang, H. ; Xu, Y. B. ; Huang, H. B.

    [S.l.] : American Institute of Physics (AIP)
    Published 1992
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    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Bilayers Fe/Au-Cu and Fe/Ag-Au made by vacuum evaporation were studied. The magneto-optical polar Kerr rotation and reflectivity spectra were measured in the region from 400 to 700 nm. In the magneto-optical Kerr rotation spectra of bilayers Fe/Au-Cu and Fe/Ag-Au with the thickness of Fe layer less than the light penetration depth, there is a broad enhancement of the magneto-optical polar Kerr rotation with a Kerr peak near the plasma edge in the reflectivity spectra of Au-Cu and Ag-Au alloys. The peak shifts toward the long wavelength side with increasing Cu and Au content in Au-Cu and Ag-Au alloys, respectively. Our results show that the composition of the reflector in our bilayer structures can shift the wavelength range of the magneto-optical Kerr rotation enhancement. Interpretation and discussions are given.
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    Articles: DFG German National Licenses
  7. 7
    Gardiner, S. ; Rothman, J. ; Xu, Y. B. ; Tselepi, M. ; Bland, J. A. C.

    [S.l.] : American Institute of Physics (AIP)
    Published 2001
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Real time resolved scanning Kerr microscopy has been used to study the switching dynamics of 50 μm diameter epitaxial Fe(100) disks. The measurements were performed using a sinusoidal sweeping field with a sweep rate of dH/dt=10 kOe/s. By performing repetitive one-shot measurements, we have mapped the statistical fluctuations and the probability distribution of characteristic switching parameters as the switching instant t0, and the switching speed, V. We observe a substantial difference in the parameters estimated from the average of several measurements compared to the parameters extracted from the probability distributions. This illustrates the potential risks of using averaging techniques in dynamic measurements, in addition to the loss of the statistical information. The disks were found to display an inhomogeneous switching, which is believed to be caused by defect damped motion of the domain walls and a inhomogeneous distribution of defects. © 2001 American Institute of Physics.
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    Articles: DFG German National Licenses
  8. 8
    Moore, T. A. ; Rothman, J. ; Xu, Y. B. ; Bland, J. A. C.

    [S.l.] : American Institute of Physics (AIP)
    Published 2001
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The dynamic hysteresis scaling behavior in epitaxial Fe/GaAs(001) and Fe/InAs(001) thin films (thickness range 7.3–150 Å) has been investigated as a function of Fe film thickness in the field sweep rate range 0.005–1000 kOe/s using the magneto-optic Kerr effect. The hysteresis loop area A follows the scaling relation A∝(dH/dt)α. We find two distinct dynamic regimes: the low dynamic regime in the sweep rate range 0.005–250 kOe/s, and the high dynamic regime beyond 250 kOe/s. There is a marked increase in α between the low and high dynamic regimes which we attribute to the dominant reversal mechanism changing from domain wall motion to nucleation. In the low dynamic regime α is a decreasing function of Fe film thickness, and this behavior is attributed to the effect of interface-induced pinning. © 2001 American Institute of Physics.
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    Articles: DFG German National Licenses
  9. 9
    Xu, Y. B. ; Hirohata, A. ; Lopez-Diaz, L. ; Leung, H. T. ; Tselepi, M. ; Gardiner, S. M. ; Lee, W. Y. ; Bland, J. A. C.

    [S.l.] : American Institute of Physics (AIP)
    Published 2000
    Staff View
    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.
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    Articles: DFG German National Licenses
  10. 10
    Xu, Y. B. ; Greig, D.

    [S.l.] : American Institute of Physics (AIP)
    Published 2000
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The partial spin-dependent densities of states (DOS) of both the iron and the boron in Fe–B amorphous magnetic alloys have been determined from spin-resolved photoemission using a synchrotron radiation source. The spin-integrated energy distribution curves (EDCs), polarization spectra and the spin-resolved EDCs show distinct differences between 15 and 40 eV photon energies due to strikingly different photon energy dependencies of the cross sections of Fe-d and B-p states. The B-p states were found to hybridize with Fe-d states and occupy a binding energy range of about 1–5.5 eV with a negative polarization; i.e., the B moment is "antiferromagetically" coupled with that of the Fe-d moment. © 2000 American Institute of Physics.
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  11. 11
    Xu, Y. B. ; Freeland, D. J. ; Tselepi, M. ; Bland, J. A. C.

    [S.l.] : American Institute of Physics (AIP)
    Published 2000
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The evolution of the uniaxial magnetic anisotropy of ultrathin epitaxial Fe films grown on InAs(100)-4×2 and GaAs(100)-4×2 has been studied in situ by means of the magneto-optical Kerr effect. In Fe/InAs(100)-4×2, the uniaxial magnetic anisotropy easy axis direction along [011] was found to be rotated 90° compared with that of Fe/GaAs(100)-4×2 along [01¯1]. Real-time reflection high energy electron diffraction measurements of Fe/InAs(100)-4×2 show that the lattice constant of the epitaxial Fe films relaxes remarkedly faster along the [01¯1] direction than along the [011] direction in the same thickness range where the uniaxial magnetic anisotropy occurs. These results suggest that the symmetry-breaking atomic scale structure of the reconstructed semiconductor surface gives rise to the uniaxial magnetic anisotropy in a ferromagnetic metal/semiconductor heterostructure via surface magneto-elastic interactions. © 2000 American Institute of Physics.
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  12. 12
    Xu, Y. B. ; Freeland, D. J. ; Kernohan, E. T. M. ; Lee, W. Y. ; Tselepi, M. ; Guertler, C. M. ; Vaz, C. A. F. ; Bland, J. A. C.

    [S.l.] : American Institute of Physics (AIP)
    Published 1999
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    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    We report on the following new ferromagnetic metal/semiconductor heterostructure material systems: (1) Fe/InAs(100)-4×2, (2) Fe/InAs(graded)/GaAs(100), and (3) Fe/InAs/AlSb/GaSb/AlSb/InAs/GaAs resonant tunneling diodes. Single crystal Fe films have been stabilized in these structures using molecular beam epitaxy growth, as evidenced by low energy electron diffraction. The magnetic and electrical properties have been studied using in situ (and focused) magneto-optical Kerr effect, alternating gradient field magnetometry, and current–voltage measurements. The results show that Fe/InAs based heterostructures are very promising systems for use in future magnetoelectronic devices as they have well defined magnetic properties as well as favorable electrical properties. © 1999 American Institute of Physics.
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  13. 13
    Hirohata, A. ; Xu, Y. B. ; Yao, C. C. ; Leung, H. T. ; Lee, W. Y. ; Gardiner, S. M. ; Hasko, D. G. ; Bland, J. A. C.

    [S.l.] : American Institute of Physics (AIP)
    Published 2000
    Staff View
    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.
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  14. 14
    Lee, W. Y. ; Yao, C. C. ; Hirohata, A. ; Xu, Y. B. ; Leung, H. T. ; Gardiner, S. M. ; McPhail, S. ; Choi, B. C. ; Hasko, D. G. ; Bland, J. A. C.

    [S.l.] : American Institute of Physics (AIP)
    Published 2000
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    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.
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  15. 15
    Bland, J. A. C. ; Hirohata, A. ; Guertler, C. M. ; Xu, Y. B. ; Tselepi, M.

    [S.l.] : American Institute of Physics (AIP)
    Published 2001
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    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.
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  16. 16
    Tselepi, M. ; Bode, P. J. ; Xu, Y. B. ; Wastlbauer, G. ; Hope, S. ; Bland, J. A. C.

    [S.l.] : American Institute of Physics (AIP)
    Published 2001
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    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    We report on the effect of oxygen on the CO-induced 90° spin switching in the Co/Cu(110) system [Hope et al., Phys. Rev. B 57, 7454 (1998)]. The epitaxial fcc Co films were grown on the unsaturated Cu(110)-{2×1}O surface and their magnetic properties have been studied with in situ magneto-optic Kerr effect. The easy axis switch of the Co(110) films is suppressed when Co is grown on O exposed Cu surfaces. Scanning tunneling microscopy images of the film surface reveals the growth of elongated nanostructures preferentially oriented along the [001] direction, providing step-like edges for gas adsorption. The density of steps is similar to the density developing during growth on the clean Cu(110) surface but the step edges now run in the perpendicular direction. The suppression of the easy axis switch can be attributed to subtle changes of the number and adsorption probability of the available atop adsorption sites along the step edges for CO chemisorption. Our experiments highlight the remarkable chemical sensitivity and adsorption site dependence of the easy axis switch of the Co(110) nanomagnets. © 2001 American Institute of Physics.
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  17. 17
    Xu, Y. B. ; Tselepi, M. ; Guertler, C. M. ; Vaz, C. A. F. ; Wastlbauer, G. ; Bland, J. A. C.

    [S.l.] : American Institute of Physics (AIP)
    Published 2001
    Staff View
    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The spin and orbital magnetic moments and the perpendicular magnetic anisotropy of 8 and 33 monolayer epitaxial bcc Fe films grown on GaAs(100)-4×6 have been measured using x-ray magnetic circular dichronism and polar magneto-optical Kerr effect. Both the films have approximately the same spin moments of about 2.0μB close to that of the bulk value. The ultrathin film shows a giant orbital moment enhancement of about 300% with respect to the bulk value and a perpendicular interface anisotropy field HsFe–GaAs of the order of −5×104 Oe. This may be partially due to an increased degree of localization of electronic states at the Fe/GaAs interface associated with the atomic scale interface structure. © 2001 American Institute of Physics.
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  18. 18
    Lee, W. Y. ; Xu, Y. B. ; Gardiner, S. M. ; Bland, J. A. C.

    [S.l.] : American Institute of Physics (AIP)
    Published 2000
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    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    We present the magnetization reversal dynamics of epitaxial Fe thin films grown on GaAs(001) and InAs(001) studied as a function of field sweep rate in the range 0.01–160 kOe/s using magneto-optic Kerr effect. For 55 and 250 Å Fe/GaAs(001), we find that the hysteresis loop area A follows the scaling relation A∝H(overdot)α with α=0.03–0.05 at low sweep rates and 0.33–0.40 at high sweep rates. For the 150 Å Fe/InAs(001) film, α is found to be ∼0.02 at low sweep rates and ∼0.17 at high sweep rates. The differing values of α are attributed to a change of the magnetization reversal process with increasing sweep rate. © 2000 American Institute of Physics.
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  19. 19
    Lee, W. Y. ; Gardelis, S. ; Choi, B.-C. ; Xu, Y. B. ; Smith, C. G. ; Barnes, C. H. W. ; Ritchie, D. A. ; Linfield, E. H. ; Bland, J. A. C.

    [S.l.] : American Institute of Physics (AIP)
    Published 1999
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    ISSN:
    1089-7550
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    We have investigated the magnetization reversal and magnetoresistance (MR) behavior of a lateral spin-injection device. The device consists of a two-dimensional electron gas (2DEG) system in an InAs quantum well and two ferromagnetic (Ni80Fe20) contacts: an injector (source) and a detector (drain). Spin-polarized electrons are injected from the first contact and propagating through InAs are collected by the second contact. By engineering the shape of the permalloy film distinct switching fields (Hc) from the injector and the collector have been observed by scanning Kerr microscopy and MR measurements. Magneto-optic Kerr effect (MOKE) hysteresis loops demonstrate that there is a range of magnetic field (20–60 Oe), at room temperature, over which magnetization in one contact is aligned antiparallel to that in the other. The MOKE results are consistent with the variation of the magnetoresistance in the spin-injection device. © 1999 American Institute of Physics.
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  20. 20
    Hirohata, A. ; Xu, Y. B. ; Guertler, C. M. ; Bland, J. A. C.

    [S.l.] : American Institute of Physics (AIP)
    Published 1999
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    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.
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