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9 Jul 2012

Volume 101, Issue 2, Articles (02xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 101, 023101 (2012); http://dx.doi.org/10.1063/1.4731792 (4 pages)

Feng Wang, Ayan Chakrabarty, Fred Minkowski, Kai Sun, and Qi-Huo Wei
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Determination of the thermal conductivity tensor of the n = 7 Aurivillius phase Sr4Bi4Ti7O24

M. A. Zurbuchen, D. G. Cahill, J. Schubert, Y. Jia, and D. G. Schlom

Appl. Phys. Lett. 101, 021904 (2012); http://dx.doi.org/10.1063/1.4733616 (4 pages)

Online Publication Date: 11 July 2012

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A challenge in the preparation of advanced materials that exist only as thin films is to establish their properties, particularly when the materials are of low symmetry or the tensor properties of interest are of high rank. Using Sr4Bi4Ti7O24 as an example, we show how the preparation of oriented epitaxial films of multiple orientations enables the thermal conductivity tensor of this tetragonal material with a c-axis length of 64.7 Å to be measured. The thermal conductivity tensor coefficients k33 = 1.10 W m−1 K−1 and k11 = k22 = 1.80 W m−1 K−1 were determined by growing epitaxial Sr4Bi4Ti7O24 films on (100), (110), and (111) SrTiO3 substrates.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
68.55.at Other materials
81.15.Fg Pulsed laser ablation deposition

Bonding and diffusion of nitrogen in the InSbN alloys fabricated by two-step ion implantation

Y. Wang, D. H. Zhang, X. Z. Chen, Y. J. Jin, J. H. Li, C. J. Liu, A. T. S. Wee, Sam Zhang, and A. Ramam

Appl. Phys. Lett. 101, 021905 (2012); http://dx.doi.org/10.1063/1.4734507 (4 pages) | Cited 1 time

Online Publication Date: 12 July 2012

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We report bonding and diffusion behavior of nitrogen incorporated into InSb wafer by two-step implantation. Three nitrogen-containing regions, i.e., a surface accumulation region, a uniform region, and a tail region, were observed in the samples after post annealing. X-ray photoelectron spectroscopy measurements at different depths reveal that majority of the nitrogen forms In-N bonds in the uniform region but exists as interstitial defects in the tail region. The diffusion coefficients of nitrogen in InSb were obtained by fitting the modified Fick’s law with experimental data and the activation energy of 0.55 ± 0.04 eV extracted confirms the interstitial dominating diffusion of nitrogen in the InSb wafer.
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66.30.J- Diffusion of impurities
79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.05.Hd Other semiconductors
61.72.jj Interstitials
61.72.sh Impurity distribution
61.72.up Other materials

Strain induced phase transition in CdSe nanowires: Effect of size and temperature

Taraknath Mandal

Appl. Phys. Lett. 101, 021906 (2012); http://dx.doi.org/10.1063/1.4734990 (4 pages) | Cited 3 times

Online Publication Date: 12 July 2012

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Using all-atom molecular dynamics simulation, we have studied the effect of size and temperature on the strain induced phase transition of wurtzite CdSe nanowires. The wurtzite structure transforms into a five-fold coordinated structure under uniaxial strain along the c axis. Our results show that lower temperature and smaller size of the nanowires stabilize the five-fold coordinated phase which is not a stable structure in bulk CdSe. High reversibility of this transformation with a very small heat loss will make these nanowires suitable for building efficient nanodevices.
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81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
64.70.kg Semiconductors
81.07.Gf Nanowires
64.70.Nd Structural transitions in nanoscale materials

Epitaxial strain-induced changes in the cation distribution and resistivity of Fe-doped CoFe2O4

J. A. Moyer, D. P. Kumah, C. A. F. Vaz, D. A. Arena, and V. E. Henrich

Appl. Phys. Lett. 101, 021907 (2012); http://dx.doi.org/10.1063/1.4735233 (4 pages) | Cited 3 times

Online Publication Date: 12 July 2012

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The distribution of cations in Fe-doped cobalt ferrite (Co1−xFe2+xO4) is investigated as a function of epitaxial strain through x-ray absorption measurements of samples grown on SrTiO3, MgO, and CoCr2O4-buffered MgAl2O4 (001). In agreement with recent theoretical calculations, compressive (tensile) strain results in the films having a larger (smaller) degree of cation inversion for iron doping levels up to x = 0.62. Measurements of the resistivity further conclude that the degree of cation inversion has a direct effect on the size of the bandgap for stoichiometric CoFe2O4, an effect that is reduced as the iron doping level is increased.
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68.60.Bs Mechanical and acoustical properties
73.61.Ng Insulators
78.70.Dm X-ray absorption spectra
81.40.Lm Deformation, plasticity, and creep
61.72.up Other materials
62.20.F- Deformation and plasticity

Estimating the pressure of laser-induced plasma shockwave by stimulated Raman shift of lattice translational modes

Zhanlong Li, Xiaoning Shan, Zuowei Li, Junsheng Cao, Mi Zhou, Yiding Wang, Zhiwei Men, and Chenglin Sun

Appl. Phys. Lett. 101, 021908 (2012); http://dx.doi.org/10.1063/1.4736410 (3 pages)

Online Publication Date: 13 July 2012

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The current paper investigates stimulated Raman scattering (SRS) when laser-induced plasma is formed in heavy water by focusing an intense pulsed 532 nm Nd:YAG laser beam at room temperature. An unexpected low-frequency SRS line attributed to the lattice translational modes of ice-VII (D2O) is observed. The pressure of the plasma shockwave is estimated using low-frequency SRS line shift.
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52.35.Tc Shock waves and discontinuities
52.38.Bv Rayleigh scattering; stimulated Brillouin and Raman scattering
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Atomic packing and short to medium range order in a U-Fe metallic glass

Y. Zhang, N. Mattern, T. X. Liang, Q. Huang, and J. Eckert

Appl. Phys. Lett. 101, 021909 (2012); http://dx.doi.org/10.1063/1.4736563 (4 pages)

Online Publication Date: 13 July 2012

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The atomic structure of the U85.7Fe14.3 metallic glasses is studied in terms of topological short range order, chemical short range order and medium range order using reverse Monte Carlo simulations. The existence of solute-centered clusters and Fe-enriched clusters clearly demonstrates a strong chemical short range order in both glasses. Two major types of medium range order are detected, one is the Fe-enriched super-clusters and the other is the close packing of the solute-centered clusters. Nevertheless, no existing model can be employed to fully describe the medium range order in U-based metallic glasses, indicating the structural complexity of these metallic glasses.
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61.43.Fs Glasses

Transmission enhancement of acoustic waves through a thin hard plate embedded with elastic inclusions

Rui Hao, Chunyin Qiu, Yangtao Ye, Chunhui Li, Han Jia, Manzhu Ke, and Zhengyou Liu

Appl. Phys. Lett. 101, 021910 (2012); http://dx.doi.org/10.1063/1.4736564 (4 pages)

Online Publication Date: 13 July 2012

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We study the transmission response of acoustic waves through a water-immersed thin hard plate embedded with elastic inclusions. The transmission spectra show a striking peak at the subwavelength region, whose position is almost irrelevant with the incident angle. Our study states that the transmission enhancement stems from the resonant excitation of the localized bending mode in the inclusion. Different from the well-known Fabry-Perot effect, here the resonant frequency reduces rapidly as the sample is thinned down. The theory is further validated by experiment. Potential applications of the abnormal transmission effect produced by such thin plate structures can be anticipated.
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43.20.Gp Reflection, refraction, diffraction, interference, and scattering of elastic and poroelastic waves
46.40.Cd Mechanical wave propagation (including diffraction, scattering, and dispersion)
62.65.+k Acoustical properties of solids

A thermophone on porous polymeric substrate

G. Chitnis, A. Kim, S. H. Song, A. M. Jessop, J. S. Bolton, and B. Ziaie

Appl. Phys. Lett. 101, 021911 (2012); http://dx.doi.org/10.1063/1.4737005 (4 pages) | Cited 1 time

Online Publication Date: 13 July 2012

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In this Letter, we present a simple, low-temperature method for fabricating a wide-band (>80 kHz) thermo-acoustic sound generator on a porous polymeric substrate. We were able to achieve up to 80 dB of sound pressure level with an input power of 0.511 W. No significant surface temperature increase was observed in the device even at an input power level of 2.5 W. Wide-band ultrasonic performance, simplicity of structure, and scalability of the fabrication process make this device suitable for many ranging and imaging applications.
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43.38.-p Transduction; acoustical devices for the generation and reproduction of sound
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
43.35.Yb Ultrasonic instrumentation and measurement techniques
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Power factor enhancement in light valence band p-type skutterudites

Jiong Yang, R. Liu, Z. Chen, L. Xi, Jihui Yang, W. Zhang, and L. Chen

Appl. Phys. Lett. 101, 022101 (2012); http://dx.doi.org/10.1063/1.4733663 (4 pages) | Cited 2 times

Online Publication Date: 9 July 2012

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The heavy band feature in 3d p-type skutterudites causes strong electron-phonon interactions and reduces the power factor. We present band structures of Ru- and Os-containing skutterudites, which show that valence band near the Fermi levels composed of 4d or 5d states is much lighter. In these skutterudites, high Seebeck coefficient can be achieved at low hole concentrations, while the corresponding density of states at the Fermi level as well as electron-phonon interactions are greatly reduced. We demonstrate that LaIr1Os3Sb12 could possess sufficiently high Seebeck coefficient, and its power factor at high temperatures is estimated to be over 50 μW cm−1K−2.
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72.15.Jf Thermoelectric and thermomagnetic effects
71.20.Gj Other metals and alloys
63.20.kd Phonon-electron interactions

Substrate orientation dependent fine structure splitting of symmetric In(Ga)As/GaAs quantum dots

J. Treu, C. Schneider, A. Huggenberger, T. Braun, S. Reitzenstein, S. Höfling, and M. Kamp

Appl. Phys. Lett. 101, 022102 (2012); http://dx.doi.org/10.1063/1.4733664 (4 pages) | Cited 4 times

Online Publication Date: 10 July 2012

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We present a comparative investigation of the fine structure splitting (FSS) from self-organized In(Ga)As quantum dots (QDs) grown on GaAs substrates with different lattice orientations. QDs grown on (111)B- and (112) oriented substrates are analyzed and compared to small QDs on commonly used (001) substrates. Mean values for the FSS as low as (5.6 ± 0.6) μeV are obtained for QDs on (111)B-GaAs, comparing favorably to the other two approaches ((11.8 ± 1.7) μeV for (112)-surfaces and (14.0 ± 2.2) μeV for (001)-surfaces). Single photon emission from (111)B QDs grown by droplet epitaxy is demonstrated via photon autocorrelation studies with a g(2)(0) value of 0.07.
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81.05.Ea III-V semiconductors
81.07.Ta Quantum dots
73.21.La Quantum dots

Single-shot nuclear magnetization recovery curves with force-gradient detection

Dimitri A. Alexson, Steven A. Hickman, John A. Marohn, and Doran D. Smith

Appl. Phys. Lett. 101, 022103 (2012); http://dx.doi.org/10.1063/1.4730610 (4 pages) | Cited 1 time

Online Publication Date: 10 July 2012

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We measure the spin-lattice relaxation time as a function of sample temperature in GaAs in a real-time single-shot inversion recovery experiment using spin force gradients acting on a magnetic tipped cantilever. After inverting 69Ga spins localized near the magnet with a single 20 ms adiabatic rapid passage sweep, the spins’ magnetization recovery was passively tracked by recording the cantilever’s frequency change, which is proportional to the longitudinal component of the spins’ magnetization. The cantilever’s frequency was recorded for a time 3*T1 for sample temperatures ranging from 4.8 to 25 K. The temperature dependence was observed for the 69Ga quadrupolar relaxation interaction.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
76.60.Es Relaxation effects
75.50.Ss Magnetic recording materials

Metal-to-insulator transition in anatase TiO2 thin films induced by growth rate modulation

T. Tachikawa, M. Minohara, Y. Nakanishi, Y. Hikita, M. Yoshita, H. Akiyama, C. Bell, and H. Y. Hwang

Appl. Phys. Lett. 101, 022104 (2012); http://dx.doi.org/10.1063/1.4733724 (4 pages)

Online Publication Date: 10 July 2012

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We demonstrate control of the carrier density of single phase anatase TiO2 thin films by nearly two orders of magnitude by modulating the growth kinetics during pulsed laser deposition, under fixed thermodynamic conditions. The resistivity and the intensity of the photoluminescence spectra of these TiO2 samples, both of which correlate with the number of oxygen vacancies, are shown to depend strongly on the growth rate. A quantitative model is used to explain the carrier density changes.
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71.30.+h Metal-insulator transitions and other electronic transitions
81.15.Fg Pulsed laser ablation deposition
68.55.ag Semiconductors
61.72.jd Vacancies
78.55.Hx Other solid inorganic materials
78.66.Li Other semiconductors

Determination of graphene work function and graphene-insulator-semiconductor band alignment by internal photoemission spectroscopy

Rusen Yan, Qin Zhang, Wei Li, Irene Calizo, Tian Shen, Curt A. Richter, Angela R. Hight-Walker, Xuelei Liang, Alan Seabaugh, Debdeep Jena, Huili Grace Xing, David J. Gundlach, and N. V. Nguyen

Appl. Phys. Lett. 101, 022105 (2012); http://dx.doi.org/10.1063/1.4734955 (4 pages) | Cited 6 times

Online Publication Date: 11 July 2012

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We determined the band alignment of a graphene-insulator-semiconductor structure using internal photoemission spectroscopy. From the flatband voltage and Dirac voltage, we infer a 4.6× 1011 cm−2 negative extrinsic charge present on the graphene surface. Also, we extract the graphene work function to be 4.56 eV, in excellent agreement with theoretical and experimental values in literature. Electron and hole injection from heavily doped p-type silicon (Si) are both observed. The barrier height from the top of the valence band of Si to the bottom of the conduction band of silicon dioxide (SiO2) is found to be 4.3 eV. The small optical absorption in graphene makes it a good transparent contact to enable the direct observation of hole injection from Si to graphene. The barrier height for holes escaping from the bottom of Si conduction band to the top of SiO2 valence band is found to be 4.6 eV.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
79.60.Jv Interfaces; heterostructures; nanostructures
65.40.gh Work functions
73.30.+y Surface double layers, Schottky barriers, and work functions
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Effect of spin relaxation rate on the interfacial spin depolarization in ferromagnet/oxide/semiconductor contacts

Kun-Rok Jeon, Byoung-Chul Min, Youn-Ho Park, Young-Hun Jo, Seung-Young Park, Chang-Yup Park, and Sung-Chul Shin

Appl. Phys. Lett. 101, 022401 (2012); http://dx.doi.org/10.1063/1.4733478 (5 pages) | Cited 2 times

Online Publication Date: 9 July 2012

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Combined measurements of normal and inverted Hanle effects in CoFe/MgO/semiconductor (SC) contacts reveal the effect of spin relaxation rate on the interfacial spin depolarization (ISD) from local magnetic fields. Despite the similar ferromagnetic electrode and interfacial roughness in both CoFe/MgO/Si and CoFe/MgO/Ge contacts, we have observed clearly different features of the ISD depending on the host SC. The precession and relaxation of spins in different SCs exposed to the local fields from more or less the same ferromagnets give rise to a notably different ratio of the inverted Hanle signal to the normal one. A model calculation of the ISD, considering the spin precession due to the local field and the spin relaxation in the host SC, explains the temperature and bias dependence of the ISD consistently.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
68.35.Ct Interface structure and roughness

Electrical and thermal spin accumulation in germanium

A. Jain, C. Vergnaud, J. Peiro, J. C. Le Breton, E. Prestat, L. Louahadj, C. Portemont, C. Ducruet, V. Baltz, A. Marty, A. Barski, P. Bayle-Guillemaud, L. Vila, J.-P. Attané, E. Augendre, et al.

Appl. Phys. Lett. 101, 022402 (2012); http://dx.doi.org/10.1063/1.4733620 (4 pages) | Cited 3 times

Online Publication Date: 9 July 2012

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In this letter, we first show electrical spin injection in the germanium conduction band at room temperature and modulate the spin signal by applying a gate voltage to the channel. The corresponding signal modulation agrees well with the predictions of spin diffusion models. Then, by setting a temperature gradient between germanium and the ferromagnet, we create a thermal spin accumulation in germanium without any charge current. We show that temperature gradients yield larger spin accumulations than electrical spin injection but, due to competing microscopic effects, the thermal spin accumulation remains surprisingly unchanged under the application of a gate voltage.
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72.20.Pa Thermoelectric and thermomagnetic effects
72.20.Ht High-field and nonlinear effects
71.20.Mq Elemental semiconductors
75.30.Ds Spin waves
72.80.Cw Elemental semiconductors
72.25.Dc Spin polarized transport in semiconductors

Surface spin disorder and exchange-bias in hollow maghemite nanoparticles

Hafsa Khurshid, Wanfeng Li, Manh-Huong Phan, Pritish Mukherjee, George C. Hadjipanayis, and Hariharan Srikanth

Appl. Phys. Lett. 101, 022403 (2012); http://dx.doi.org/10.1063/1.4733621 (5 pages) | Cited 4 times

Online Publication Date: 9 July 2012

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We report a comparative study of the magnetic properties of polycrystalline hollow γ-Fe2O3 nanoparticles with two distinctly different average sizes of 9.2 ± 1.1 nm and 18.7 ± 1.5 nm. High-resolution transmission electron microscopy images reveal the presence of a shell with thickness of 2 nm and 4.5 nm for the 9.2 nm and 18.7 nm nanoparticles, respectively. The field-cooled hysteresis loops show interesting features of enhanced coercivity and horizontal and vertical shifts associated with the polarity of the cooling field for both types of nanoparticles. While the anomalously large horizontal shifts and open hysteresis loop in a field as high as 9 T observed for the 9.2 nm nanoparticles corresponds to a “minor loop” of the hysteresis loop, the loop shift observed for the 18.7 nm nanoparticles manifests an intrinsic “exchange bias” (EB). Relative to the 18.5 ± 3.2 nm solid nanoparticles, a much stronger EB effect is achieved in the 18.7 nm hollow nanoparticles. Our studies point to the importance of inner and outer surface spin disorder giving rise to surface anisotropy and EB and reveal a perspective of tuning EB in hollow magnetic nanoparticle systems.
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75.70.Rf Surface magnetism
75.30.Et Exchange and superexchange interactions
75.50.Tt Fine-particle systems; nanocrystalline materials
75.75.-c Magnetic properties of nanostructures
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Sg Magnetocaloric effect, magnetic cooling

Temperature dependence of nanometer-size metallic phase texture and its correlation with bulk magnetic and transport properties and defects of a (La0.4Pr0.6)0.67Ca0.33MnO3 film

Surendra Singh, M. R. Fitzsimmons, H. Jeen, A. Biswas, and M. E. Hawley

Appl. Phys. Lett. 101, 022404 (2012); http://dx.doi.org/10.1063/1.4733666 (4 pages)

Online Publication Date: 9 July 2012

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Using conductive atomic force microscopy, we observed non-uniform distributions of metallic and insulating domains on the surface of a single crystalline (La0.4Pr0.6)0.67Ca0.33MnO3 film grown on a (110) NdGaO3 substrate. Metallic phase texture is confined to stripes corresponding to ∼100 nm lateral dimension between terrace steps. The electronic properties of the surface exhibit thermal hysteresis, and the hysteresis is similar to that of the transport and magnetism of the film bulk.
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68.55.jm Texture
68.55.-a Thin film structure and morphology
73.61.Ng Insulators
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.16.-c Methods of micro- and nanofabrication and processing
75.75.-c Magnetic properties of nanostructures

Current-induced motion of a transverse magnetic domain wall in the presence of spin Hall effect

Soo-Man Seo, Kyoung-Whan Kim, Jisu Ryu, Hyun-Woo Lee, and Kyung-Jin Lee

Appl. Phys. Lett. 101, 022405 (2012); http://dx.doi.org/10.1063/1.4733674 (5 pages) | Cited 6 times

Online Publication Date: 9 July 2012

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We theoretically study current-induced dynamics of a transverse magnetic domain wall in bi-layer nanowires consisting of a ferromagnetic layer on top of a nonmagnetic layer with strong spin-orbit coupling. Domain wall dynamics is characterized by two threshold current densities, JthWB and JthREV, where JthWB is a threshold for the chirality switching of the domain wall and JthREV is another threshold for the reversed domain wall motion caused by spin Hall effect. Domain walls with a certain chirality may move opposite to the electron-flow direction with high speed in the current range JthREV<J<JthWB for the system designed to satisfy the conditions JthWB>JthREV and α>β, where α is the Gilbert damping constant and β is the nonadiabaticity of spin torque. Micromagnetic simulations confirm the validity of analytical results.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.60.Ch Domain walls and domain structure
72.25.-b Spin polarized transport
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Tt Fine-particle systems; nanocrystalline materials
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Enhancement of spin injection from ferromagnet to graphene with a Cu interfacial layer

Chi Zhang, Ying Wang, Baolei Wu, and Yihong Wu

Appl. Phys. Lett. 101, 022406 (2012); http://dx.doi.org/10.1063/1.4733729 (5 pages)

Online Publication Date: 9 July 2012

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We present an enhancement in spin injection from ferromagnet to multilayer graphene through the introduction of a thin Cu interfacial layer at the metal-graphene interface. A nonlocal magnetoresistance of 286 mΩ and a corresponding spin-injection efficiency of 2.46% have been obtained which are among the highest values reported so far for metal-contacted graphene spin-valve devices. The enhancement of spin-injection is attributed to a non-ohmic contact between Cu and graphene, as revealed by the temperature-dependent I-V and differential conductance measurements.
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72.25.-b Spin polarized transport
75.50.Dd Nonmetallic ferromagnetic materials
72.20.My Galvanomagnetic and other magnetotransport effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Observation of magnetic domain-wall dynamics transition in Co/Ni multilayered nanowires

Kab-Jin Kim, D. Chiba, K. Kobayashi, S. Fukami, M. Yamanouchi, H. Ohno, Soong-Geun Je, Sug-Bong Choe, and T. Ono

Appl. Phys. Lett. 101, 022407 (2012); http://dx.doi.org/10.1063/1.4733667 (4 pages)

Online Publication Date: 10 July 2012

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We observe a transition of domain-wall (DW) dynamics in ferromagnetic wires made of Co/Ni multilayers by use of transport measurement. As the wire width reduces, DW dynamics exhibits a transition from dendrite growth to pure DW motion. The threshold width is found to be about 300 nm and strongly depends on the relative dragging direction of the magnetic field and the current on DW: parallel (antiparallel) direction results in much smaller (larger) threshold width. It should be considered as a building block for DW-motion-based device applications.
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75.60.Ch Domain walls and domain structure
75.78.Fg Dynamics of domain structures
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Tt Fine-particle systems; nanocrystalline materials
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Cc Other ferromagnetic metals and alloys

Correlation between oxygen vacancies and magnetism in Mn-doped Y2O3 nanocrystals investigated by defect engineering techniques

T. S. Wu, Y. C. Chen, Y. F. Shiu, H. J. Peng, S. L. Chang, H. Y. Lee, P. P. Chu, C. W. Hsu, L. J. Chou, C. W. Pao, J. F. Lee, J. Kwo, M. Hong, and Y. L. Soo

Appl. Phys. Lett. 101, 022408 (2012); http://dx.doi.org/10.1063/1.4732094 (5 pages) | Cited 1 time

Online Publication Date: 11 July 2012

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Defect engineering techniques have been employed to generate and remove oxygen vacancy defects in nanoparticles of Y2O3:Mn diluted magnetic oxide (DMO). These samples were prepared by thermal decomposition method followed by a series of thermal annealing in oxygen and forming gas. The x-ray absorption analysis reveals that O vacancies surrounding Mn and Y atoms were appreciably increased by forming-gas-annealing and decreased by oxygen-annealing, accompanied by enhanced and reduced saturation magnetization as demonstrated by magnetic measurements, respectively. Our results demonstrate strong correlation between magnetism and O vacancies and therefore strongly support the bound magnetic polaron model for these high-k DMOs.
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61.72.jd Vacancies
71.38.-k Polarons and electron-phonon interactions
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.70.Dm X-ray absorption spectra
81.40.Gh Other heat and thermomechanical treatments

Magneto-electric tuning of the phase of propagating spin waves

Mingqiang Bao, Guodong Zhu, Kin L. Wong, Joshua L. Hockel, Mark Lewis, Jing Zhao, Tao Wu, Pedram Khalili Amiri, and Kang L. Wang

Appl. Phys. Lett. 101, 022409 (2012); http://dx.doi.org/10.1063/1.4734499 (4 pages) | Cited 2 times

Online Publication Date: 11 July 2012

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The utilization of a magnetoelectric film composite to control, by an electric field, the phase of magnetostatic surface spin waves propagating along thin films is reported. Laminates of ferromagnetic films of Ni and NiFe are deposited on a ferroelectric substrate, lead magnesium niobate-lead titanate. The phase of propagating spinwaves is shown to be modulated by an electric field while traveling a finite distance along the surface. The observed phase change in the spinwaves is in agreement with the anisotropy field changes measured with magneto optical Kerr effect hysteresis loops. A quantitative agreement is demonstrated.
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77.55.Nv Multiferroic/magnetoelectric films
75.30.Ds Spin waves
75.50.Bb Fe and its alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Ak Magnetic properties of monolayers and thin films
75.70.Rf Surface magnetism

Demonstration of laser induced magnetization reversal in GdFeCo nanostructures

L. Le Guyader, S. El Moussaoui, M. Buzzi, R. V. Chopdekar, L. J. Heyderman, A. Tsukamoto, A. Itoh, A. Kirilyuk, Th. Rasing, A. V. Kimel, and F. Nolting

Appl. Phys. Lett. 101, 022410 (2012); http://dx.doi.org/10.1063/1.4733965 (4 pages) | Cited 2 times

Online Publication Date: 12 July 2012

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Magnetization switching by a single femtosecond laser heat pulse is demonstrated for out-of-plane domains with sizes down to 200 nm in GdFeCo nanostructures. A complex magnetic domain configuration was revealed with a photoemission electron microscope employing x-ray magnetic circular dichroism at the Fe L3 edge and consisted of in-plane magnetized rims and out-of-plane domains, which results from the structuring process. No influence of this complex domain pattern on the switching efficiency of the structures was detected, constituting an important step towards the application of laser induced magnetization switching in storage devices.
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75.75.-c Magnetic properties of nanostructures
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ch Domain walls and domain structure
75.60.Jk Magnetization reversal mechanisms
75.78.-n Magnetization dynamics
75.50.Bb Fe and its alloys

Strain induced magnetic domain evolution and spin reorientation transition in epitaxial manganite films

Gyanendra Singh, P. K. Rout, Rajni Porwal, and R. C. Budhani

Appl. Phys. Lett. 101, 022411 (2012); http://dx.doi.org/10.1063/1.4734732 (4 pages) | Cited 1 time

Online Publication Date: 12 July 2012

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The evolution of magnetic domain structure in epitaxial La0.625Ca0.375MnO3 films on (001) NdGaO3 is monitored as a function of temperature and magnetic field using magnetic force microscopy. We see two distinct regions of magnetic orientational order: one in-plane displaying contrast-less image and the other tilted away from the film plane forming a distinct stripe pattern. A strong domain splitting is observed at the boundary of two regions, which is resilient to reorientation with temperature and magnetic field. We propose a model magnetic free energy functional to explain the mechanism of domain splitting seen in manganite films.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.78.Fg Dynamics of domain structures

Pressure effects on the magnetic properties of FeCuZr studied by x-ray magnetic circular dichroism: Evidence of weakening of ferromagnetism in FeCuZr alloys

A. Martínez, J. J. Romero, F. Bartolomé, L. M. García, F. Baudelet, A. Hernando, and P. Crespo

Appl. Phys. Lett. 101, 022412 (2012); http://dx.doi.org/10.1063/1.4735300 (4 pages) | Cited 1 time

Online Publication Date: 12 July 2012

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The room temperature changes of the magnetic behavior under pressure of an invar alloy of nominal composition (Fe0.5Cu0.5)87Zr13 (at. %) has been studied by K-edge x-ray magnetic circular dichroism (XMCD) and x-ray absorption near edge spectroscopy (XANES). The Curie temperature, as determined from low field magnetization measurements, is (255 ± 15)K. However XMCD shows a non negligible signal above this temperature. In addition, the XMCD signal decreases upon increasing pressure indicating a pressure-induced collapse of the magnetic moment. These results evidence the itinerant character of FeCuZr alloys as well as the occurrence of magnetovolume effects characterized by a strong dependence of the 3d band on the Fe-Fe nearest neighbor distances.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.80.+q Magnetomechanical effects, magnetostriction
78.70.Dm X-ray absorption spectra
75.30.Cr Saturation moments and magnetic susceptibilities
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Bb Fe and its alloys
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