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9 Jan 2012

Volume 100, Issue 2, Articles (02xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 100, 023701 (2012); http://dx.doi.org/10.1063/1.3673335 (3 pages)

Biswarup Pathak, Henrik Löfås, Jariyanee Prasongkit, Anton Grigoriev, Rajeev Ahuja, and Ralph H. Scheicher
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(Si)5−2y(AlP)y alloys assembled on Si(100) from Al-P-Si3 building units

T. Watkins, L. Jiang, C. Xu, A. V. G. Chizmeshya, D. J. Smith, J. Menéndez, and J. Kouvetakis

Appl. Phys. Lett. 100, 022101 (2012); http://dx.doi.org/10.1063/1.3675444 (4 pages) | Cited 3 times

Online Publication Date: 9 January 2012

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An original class of IV/III-V hybrid (Si)5−2y(AlP)y/Si(100) semiconductors have been produced via tailored interactions of molecular P(SiH3)3 and atomic Al yielding tetrahedral “Al-P-Si3” building blocks. Extensive structural, optical, and vibrational characterization corroborates that these units condense to assemble single-phase, monocrystalline alloys containing 60%-90% Si (y = 0.3-1.0) as nearly defect-free layers lattice-matched to Si. Spectroscopic ellipsometry and density functional theory band structure calculations indicate mild compositional bowing of the band gaps, suggesting that the tuning needed for optoelectronic applications should be feasible.
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68.55.ag Semiconductors
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.30.Hv Other nonmetallic inorganics
78.66.Li Other semiconductors
71.20.Nr Semiconductor compounds

Noncatalytic chemical vapor deposition of graphene on high-temperature substrates for transparent electrodes

Jie Sun (孙捷), Matthew T. Cole, Niclas Lindvall, Kenneth B. K. Teo (张谋瑾), and August Yurgens

Appl. Phys. Lett. 100, 022102 (2012); http://dx.doi.org/10.1063/1.3675632 (3 pages) | Cited 13 times

Online Publication Date: 9 January 2012

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A noncatalytic chemical vapor deposition mechanism is proposed, where high precursor concentration, long deposition time, high temperature, and flat substrate are needed to grow large-area nanocrystalline graphene using hydrocarbon pyrolysis. The graphene is scalable, uniform, and with controlled thickness. It can be deposited on virtually any nonmetallic substrate that withstands ∼1000 °C. For typical examples, graphene grown directly on quartz and sapphire shows transmittance and conductivity similar to exfoliated or metal-catalyzed graphene, as evidenced by transmission spectroscopy and transport measurements. Raman spectroscopy confirms the sp2-C structure. The model and results demonstrate a promising transfer-free technique for transparent electrode production.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.63.Bd Nanocrystalline materials
78.30.Na Fullerenes and related materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
78.67.Wj Optical properties of graphene

Tuning the Schottky barrier height at MgO/metal interface

T. Jaouen, G. Jézéquel, G. Delhaye, B. Lépine, P. Turban, and P. Schieffer

Appl. Phys. Lett. 100, 022103 (2012); http://dx.doi.org/10.1063/1.3675859 (3 pages) | Cited 1 time

Online Publication Date: 9 January 2012

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We present an experimental investigation of the interface electronic structure of thin MgO films epitaxially grown on Ag(001) by x-ray and ultraviolet photoemission spectroscopy as a function of the oxide growth conditions. It is shown that the Schottky barrier height at MgO/metal interface can be tuned over 0.7 eV by a modification of the oxygen partial pressure or the sample temperature. These experimental results are explained in the framework of the extended Schottky-Mott model and the MgO-induced polarization effect by Mg enrichment of the silver surface region.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts
79.60.Jv Interfaces; heterostructures; nanostructures

Hybrid density functional theory study of band gap tuning in AlN and GaN through equibiaxial strains

Yifeng Duan, Lixia Qin, Liwei Shi, Gang Tang, and Hongliang Shi

Appl. Phys. Lett. 100, 022104 (2012); http://dx.doi.org/10.1063/1.3675864 (3 pages) | Cited 3 times

Online Publication Date: 9 January 2012

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Structural transformation and the variation in the band gap of (0001) AlN and GaN films as a function of equibiaxial in-plane strain are studied using the HSE06 range-separated hybrid functional. Although AlN and GaN under strain share the same structural transition from wurtzite to a graphitelike phase, their electronic properties are significantly different. Both wurtzite and graphitelike AlN under strain can display either direct or indirect band structures, whereas the band gap of wurtzite GaN is always direct and graphitelike GaN always indirect. Furthermore, it is more difficult for AlN than GaN to obtain the graphitelike semi-metallic phase. Our results for GaN support the conclusions obtained from standard density functional theory [Dong et al., Appl. Phys. Lett. 96, 202106 (2010)]
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71.20.Nr Semiconductor compounds
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
64.70.kg Semiconductors
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Spectral fluctuations of excitonic transitions of InGaAs single quantum dots

Wan Bak, Haneol Noh, Corey Stambaugh, Yasuhiko Arakawa, and Wonho Jhe

Appl. Phys. Lett. 100, 022105 (2012); http://dx.doi.org/10.1063/1.3676043 (3 pages)

Online Publication Date: 10 January 2012

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We report on our experimental study of spectral diffusion in grown InGaAs single quantum dots. Using a double-tapered tip, near-field scanning optical microscope, we obtain the spectral diffusion resulting from the quantum confined Stark effect of individual quantum dots in a randomly fluctuating electric field. These electric fields come from localized charges at defects in the vicinity of the quantum dots. In particular, we find that the similar-patterned temporal jitter, seen in the spectral diffusion, emits from a quantum dot and is dependent on the excitation density and applied bias voltage.
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78.67.Hc Quantum dots
05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion
66.30.-h Diffusion in solids
68.65.Hb Quantum dots (patterned in quantum wells)
71.35.-y Excitons and related phenomena
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Controllable tunnel coupling and molecular states in a graphene double quantum dot

Lin-Jun Wang, Hai-Ou Li, Tao Tu, Gang Cao, Cheng Zhou, Xiao-Jie Hao, Zhan Su, Ming Xiao, Guang-Can Guo, Albert M. Chang, and Guo-Ping Guo

Appl. Phys. Lett. 100, 022106 (2012); http://dx.doi.org/10.1063/1.3676083 (5 pages) | Cited 2 times

Online Publication Date: 10 January 2012

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We have measured a graphene double quantum dot device with multiple electrostatic gates that are used to enhance control to investigate it. At low temperatures, the transport measurements reveal honeycomb charge stability diagrams which can be tuned from weak to strong interdot tunnel coupling regimes. We precisely extract a large interdot tunnel coupling strength for this system allowing for the observation of tunnel-coupled molecular states extending over the whole double dot. This clean, highly controllable system serves as an essential building block for quantum devices in a nuclear-spin-free world.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Clustering of N impurities in ZnO

J. Furthmüller, F. Hachenberg, A. Schleife, D. Rogers, F. Hosseini Teherani, and F. Bechstedt

Appl. Phys. Lett. 100, 022107 (2012); http://dx.doi.org/10.1063/1.3675867 (3 pages) | Cited 4 times

Online Publication Date: 10 January 2012

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Ab initio density functional theory and quasiparticle calculations for the incorporation of nitrogen atoms on oxygen sites in ZnO are presented. It is demonstrated that clustering of N atoms is energetically favored over the isolated N0 substitutional impurity. Tetrahedrons of N0 give rise to promising quasiparticle band structures with impurity states slightly above the valence band maximum (VBM), which, however, shift to higher energies with increasing negative ionization. The lowest recharging level ɛ(0/−) tends to a value 0.4 eV above the VBM, which is too deep for anything other than a weak p-doping.
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71.55.Gs II-VI semiconductors
61.72.uj III-V and II-VI semiconductors
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.20.Nr Semiconductor compounds

Anisotropic electrical transport properties of poly(methyl methacrylate) infiltrated aligned carbon nanotube mats

P. Mahanandia and K. K. Nanda

Appl. Phys. Lett. 100, 022108 (2012); http://dx.doi.org/10.1063/1.3675873 (3 pages)

Online Publication Date: 10 January 2012

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We report the electrical anisotropic transport properties of poly(methyl methacrylate) infiltrated aligned carbon nanotube mats. The anisotropy in the resistivity increases with decreasing temperature and the conduction mechanism in the parallel and perpendicular direction is different. Magnetoresistance (MR) studies also suggest anisotropic behavior of the infiltrated mats. Though MR is negative, an upturn is observed when the magnetic field is increased. This is due to the interplay of electron weak localization and electron-electron interactions mechanisms. Overall, infiltrated carbon nanotube mat is a good candidate for anisotropically conductive polymer composite and a simple fabrication method has been reported.
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72.20.My Galvanomagnetic and other magnetotransport effects
72.80.Le Polymers; organic compounds (including organic semiconductors)
73.20.Fz Weak or Anderson localization
75.30.Gw Magnetic anisotropy
75.47.Pq Other materials

Effect of hafnium addition on Zn-Sn-O thin film transistors fabricated by solution process

Jun Young Choi, Sang Sig Kim, and Sang Yeol Lee

Appl. Phys. Lett. 100, 022109 (2012); http://dx.doi.org/10.1063/1.3669700 (3 pages) | Cited 4 times

Online Publication Date: 11 January 2012

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The feasibility of controlling the threshold voltage (Vth) and field effect mobility (μFE) has been studied by adjusting hafnium ratio. Hafnium zinc tin oxide (HZTO) thin films were fabricated with various hafnium ratios. Vth shifted toward positive direction, and the μFE was decreased due to the decrease of carrier concentration, because hafnium acts as carrier suppressor. The subthreshold swing exhibits good properties from 1.01 to 0.44. The decrease of carrier concentration in HZTO is closely related with the decrease of the number of oxygen by hafnium ion.
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85.30.Tv Field effect devices
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.55.ag Semiconductors

Charge separation in CdSe/CdTe hetero-nanowires measured by electrostatic force microscopy

Sebastian Schäfer, Aina Reich, Zhe Wang, Tobias Kipp, and Alf Mews

Appl. Phys. Lett. 100, 022110 (2012); http://dx.doi.org/10.1063/1.3676278 (3 pages) | Cited 2 times

Online Publication Date: 12 January 2012

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The charge state of free standing axial type-II CdSe/CdTe hetero-nanowires is monitored via electrostatic force microscopy. The CdSe and the CdTe segment which are identified by Raman spectroscopy are found to be negatively and positively charged, respectively. The charge state is monitored without and with local illumination. We found that the magnitude of opposite charging in the respective nanowire segment is increasing with illumination power, which is attributed to a charge separation of the photogenerated electron-hole pairs across the CdSe/CdTe interface.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.30.Fs III-V and II-VI semiconductors
73.21.Hb Quantum wires

Top-gate thin-film transistors based on GaN channel layer

Rongsheng Chen, Wei Zhou, and Hoi Sing Kwok

Appl. Phys. Lett. 100, 022111 (2012); http://dx.doi.org/10.1063/1.3676447 (3 pages) | Cited 1 time

Online Publication Date: 13 January 2012

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Gallium nitride (GaN) thin films were utilized as active channel layer to produce top-gate n-type thin-film transistors (TFTs). GaN thin films with wurtzite structure were deposited by reactive DC magnetron sputtering technique at room temperature using liquid gallium target. The GaN TFTs exhibit good electrical performance such as field effect mobility of 1 cm2/Vs, threshold voltage of −0.4 V, on/off current ratio of 105, and subthreshold swing of 0.8 V/decade.
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85.30.Tv Field effect devices
81.15.Cd Deposition by sputtering

Anisotropy of free-carrier absorption and diffusivity in m-plane GaN

P. Ščajev, K. Jarašiūnas, Ü. Özgür, H. Morkoç, J. Leach, and T. Paskova

Appl. Phys. Lett. 100, 022112 (2012); http://dx.doi.org/10.1063/1.3674306 (4 pages)

Online Publication Date: 13 January 2012

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Polarization-dependent free-carrier absorption (FCA) in bulk m-plane GaN at 1053 nm revealed approximately 6 times stronger hole-related absorption for E⊥c than for E||c probe polarization both at low and high carrier injection levels. In contrast, FCA at 527 nm was found isotropic at low injection levels due to electron resonant transitions between the upper and lower conduction bands, whereas the anisotropic impact of holes was present only at high injection levels by temporarily blocking electron transitions. Carrier transport was also found to be anisotropic under two-photon excitation, with a ratio of 1.17 for diffusivity perpendicular and parallel to the c-axis.
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78.30.Fs III-V and II-VI semiconductors
81.05.Ea III-V semiconductors
79.20.Ws Multiphoton absorption
66.30.-h Diffusion in solids
71.20.Nr Semiconductor compounds

Ohmic contacts to n-type germanium with low specific contact resistivity

K. Gallacher, P. Velha, D. J. Paul, I. MacLaren, M. Myronov, and D. R. Leadley

Appl. Phys. Lett. 100, 022113 (2012); http://dx.doi.org/10.1063/1.3676667 (3 pages) | Cited 5 times

Online Publication Date: 13 January 2012

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A low temperature nickel process has been developed that produces Ohmic contacts to n-type germanium with specific contact resistivities down to (2.3 ± 1.8) × 10−7 Ω-cm2 for anneal temperatures of 340 °C. The low contact resistivity is attributed to the low resistivity NiGe phase which was identified using electron diffraction in a transmission electron microscope. Electrical results indicate that the linear Ohmic behaviour of the contact is attributed to quantum mechanical tunnelling through the Schottky barrier formed between the NiGe alloy and the heavily doped n-Ge.
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73.40.Ns Metal-nonmetal contacts
61.72.Cc Kinetics of defect formation and annealing
73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Cg Contact resistance, contact potential
73.40.Gk Tunneling
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Electric field induced magnetization rotation in patterned Ni ring/Pb(Mg1/3Nb2/3)O3](1−0.32)-[PbTiO3]0.32 heterostructures

Joshua L. Hockel, Alexandre Bur, Tao Wu, Kyle P. Wetzlar, and Gregory P. Carman

Appl. Phys. Lett. 100, 022401 (2012); http://dx.doi.org/10.1063/1.3675458 (3 pages) | Cited 3 times

Online Publication Date: 9 January 2012

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Electric field induced magnetoelastic anisotropy is shown to rotate the magnetization of a ring-shaped magnet by 90° in a Ni ring/(011) Pb(Mg1/3Nb2/3)O3](1−0.32)-[PbTiO3]0.32 heterostructure. The 2000 nm diameter ring is initially field annealed forming the “onion” magnetization state. A 0.8 MV/m electric field is applied to the substrate creating anisotropic piezostrain and a perpendicular in-plane easy axis. Magnetic force microscopy confirms the 90° rotation of the vortex-type domain walls from the field annealing direction. Rotations are stable without electric field due to remnant strains induced during the poling process, supporting the viability of strain-based magnetic recording methods.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.80.+q Magnetomechanical effects, magnetostriction
75.30.Gw Magnetic anisotropy
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ch Domain walls and domain structure
77.22.Ej Polarization and depolarization

All-oxide system for spin pumping

Z. Qiu, Y. Kajiwara, K. Ando, Y. Fujikawa, K. Uchida, T. Tashiro, K. Harii, T. Yoshino, and E. Saitoh

Appl. Phys. Lett. 100, 022402 (2012); http://dx.doi.org/10.1063/1.3675463 (3 pages) | Cited 2 times

Online Publication Date: 9 January 2012

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In a simple all-oxide system, spin pumping driven by spin wave resonances have been investigated by using the inverse spin-Hall effect (ISHE). In a lanthanum doped yttrium iron garnet (La:YIG)/indium tin oxide (ITO) bilayer film, the spin pumping generates and injects a spin current into the ITO layer, and an electromotive force signal is observed via the ISHE. The electromotive forces were measured depend on the out-of-plane magnetic-field-angle and the microwave excitation power, which were consistent with the theoretical prediction of the ISHE. The realization of the all-oxide spin pumping system extends possibilities for the oxide spintronics.
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72.25.Dc Spin polarized transport in semiconductors
72.25.-b Spin polarized transport
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
68.65.Ac Multilayers
73.21.Ac Multilayers
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Tuning of magnetization relaxation in ferromagnetic thin films through seed layers

Lei Lu, Jared Young, Mingzhong Wu, Christoph Mathieu, Matthew Hadley, Pavol Krivosik, and Nan Mo

Appl. Phys. Lett. 100, 022403 (2012); http://dx.doi.org/10.1063/1.3675614 (3 pages) | Cited 3 times

Online Publication Date: 9 January 2012

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Tuning of the magnetization relaxation in Fe65Co35 thin films via seed layers was demonstrated. Through the use of different types of seed layers, one can tune substantially both the magnitude and frequency dependence of the relaxation rate η of the film. This tuning relies on the change of the film grain properties with the seed layer and the correlation between grain properties and two-magnon scattering processes. In spite of a significant change of η with the seed layer, the film static magnetic properties remain relatively constant.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Ak Magnetic properties of monolayers and thin films
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.30.Ds Spin waves
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
75.50.Bb Fe and its alloys

Ultrasensitive anomalous Hall effect in SiO2/Fe-Pt/SiO2 sandwich structure films

Y. M. Lu, J. W. Cai, H. Y. Pan, and Li Sun

Appl. Phys. Lett. 100, 022404 (2012); http://dx.doi.org/10.1063/1.3672046 (4 pages) | Cited 2 times

Online Publication Date: 10 January 2012

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Ultrasensitive anomalous Hall effect has been demonstrated in a SiO2/Fe-Pt/SiO2 sandwich structure. Owing to the interfacial electron scattering, the Hall resistivity is appreciably enhanced for the thin Fe-Pt layers of high quality; meanwhile, a large interfacial anisotropy is formed and further enhanced through annealing, leading to a room temperature Hall slope up to 2160 μΩ cm/T and field sensitivity of 12 000 Ω/T at Fe-Pt thickness ∼1.8 nm. This number is an order magnitude higher than the best semiconductor sensitivity. Other important technical characteristics, such as electrical resistivity and temperature coefficient, are also suitable to practical magnetic Hall sensor development.
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73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.40.Ns Metal-nonmetal contacts
81.40.Gh Other heat and thermomechanical treatments
73.61.-r Electrical properties of specific thin films

Thickness-dependent voltage-modulated magnetism in multiferroic heterostructures

Li Shu, Zheng Li, Jing Ma, Ya Gao, Lin Gu, Yang Shen, Yuanhua Lin, and C. W. Nan

Appl. Phys. Lett. 100, 022405 (2012); http://dx.doi.org/10.1063/1.3675868 (4 pages) | Cited 5 times

Online Publication Date: 10 January 2012

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The voltage-modulated magnetic behavior in multiferroic Ni/BaTiO3 heterostructures grown on SrTiO3 single crystal substrate was observed by the magneto-optical Kerr effect measurement in an AC modulation technique with synchronizing the frequency of the Kerr signal detector to the low-frequency AC actuation voltage. The results showed coexistence at room-temperature of two magnetoelectric (ME) mechanisms, i.e., strain- and interface charge-mediated couplings. The interaction between the different ME couplings leads to a remarkable thickness-dependent voltage modulation of the magnetic behavior.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
78.20.Ls Magneto-optical effects
75.85.+t Magnetoelectric effects, multiferroics

Antiferromagnetic coupling across silicon regulated by tunneling currents

R. R. Gareev, M. Schmid, J. Vancea, C. H. Back, R. Schreiber, D. Bürgler, C. M. Schneider, F. Stromberg, and H. Wende

Appl. Phys. Lett. 100, 022406 (2012); http://dx.doi.org/10.1063/1.3675872 (3 pages)

Online Publication Date: 10 January 2012

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We report on the enhancement of antiferromagnetic coupling in epitaxial Fe/Si/Fe structures by voltage-driven spin-polarized tunneling currents. Using the ballistic electron magnetic microscopy, we established that the hot-electron collector current reflects magnetization alignment and the magnetocurrent exceeds 200% at room temperature. The saturation magnetic field for the collector current corresponding to the parallel alignment of magnetizations rises up with the tunneling current, thus demonstrating stabilization of the antiparallel alignment and increasing antiferromagnetic coupling. We connect the enhancement of antiferromagnetic coupling with local dynamic spin torques mediated by spin-polarized tunneling electrons.
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73.40.Ns Metal-nonmetal contacts
75.50.Ee Antiferromagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
72.20.Ht High-field and nonlinear effects
72.20.My Galvanomagnetic and other magnetotransport effects
72.25.-b Spin polarized transport

Direct observation of magnetic phase coexistence and magnetization reversal in a Gd0.67Ca0.33MnO3 thin film

Jeehoon Kim, N. Haberkorn, Leonardo Civale, Evgeny Nazaretski, Paul Dowden, Avadh Saxena, J. D. Thompson, and Roman Movshovich

Appl. Phys. Lett. 100, 022407 (2012); http://dx.doi.org/10.1063/1.3676045 (4 pages) | Cited 1 time

Online Publication Date: 11 January 2012

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We have investigated the ferrimagnetic domain structure in a Gd0.67Ca0.33MnO3 thin film using magnetic force microscopy. We observe clear signs of phase separation, with magnetic islands embedded in a non-magnetic matrix. We also directly visualize the reversal of magnetization of ferrimagnetic domains as a function of temperature and attribute it to a change in the balance of magnetization of anti-aligned Mn and Gd sublattices.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.50.Gg Ferrimagnetics
75.60.Jk Magnetization reversal mechanisms
75.70.Ak Magnetic properties of monolayers and thin films

Magnetic and transport properties of Mn3−xGa/MgO/Mn3−xGa magnetic tunnel junctions: A first-principles study

Zhaoqiang Bai, Yongqing Cai, Lei Shen, Ming Yang, Viloane Ko, Guchang Han, and Yuanping Feng

Appl. Phys. Lett. 100, 022408 (2012); http://dx.doi.org/10.1063/1.3676195 (5 pages) | Cited 6 times

Online Publication Date: 11 January 2012

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Magnetic and transport properties of Mn3−xGa/MgO/Mn3−xGa (0 ≤ x ≤ 1) magnetic tunnel junctions are studied using first-principles approach based on density functional theory and non-equilibrium Green’s function. Perpendicular magnetization, of which the magnetic anisotropy energy reaches more than 1 meV/unit-cell, is confirmed to be energetically favoured by both Mn2Ga and Mn3Ga thin films. Furthermore, despite high spin-polarization at the Fermi energy for both these compounds as reported, our transport calculation shows considerable disparity in the transmission behaviour between Mn2Ga/MgO/Mn2Ga(001) and Mn3Ga/MgO/Mn3Ga(001) magnetic tunnel junctions: huge optimistic tunneling magnetoresistance ratio of 103% for the former, and nevertheless, no tunneling magnetoresistance effect absolutely for the latter. This phenomenon is attributed to the symmetry selective filtering effect of the MgO spacer. On this premise, Mn3−xGa compounds with low Mn concentration are predicted to be promising candidate materials to serve as the electrodes of spin-transfer torque devices in the next-generation data storage technique.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.76.+j Spin transport effects
72.25.-b Spin polarized transport
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.30.Gw Magnetic anisotropy

Towards compact three-dimensional magnetoelectronics—Magnetoresistance in rolled-up Co/Cu nanomembranes

C. Müller, C. C. Bof Bufon, M. E. Navarro Fuentes, D. Makarov, D. H. Mosca, and O. G. Schmidt

Appl. Phys. Lett. 100, 022409 (2012); http://dx.doi.org/10.1063/1.3676269 (4 pages) | Cited 3 times

Online Publication Date: 11 January 2012

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Strain engineering combined with standard top-down techniques is shown to be eligible to fabricate compact three dimensional architectures based on rolled-up Co/Cu nanomembranes. The fabrication process is fully integrative and provides rolled-up tubes of high quality and yield (∼95%). Rolled-up tubes with two windings show magnetoresistances (MR) ∼20% higher than those observed in thin films. The enhancement of magnetoresistance is most likely due to the coupling between neighboring windings, variations of the Cu layer thickness, and increased effective area crossed by current lines in the film plane. Present results inhere new potential for magnetic sensing and electronic components.
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72.15.Gd Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.70.Ak Magnetic properties of monolayers and thin films
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.75.Cd Fabrication of magnetic nanostructures
68.65.Ac Multilayers
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Ambient effects on electric-field-induced local charge modification of TiO2

Haeri Kim, Seungbum Hong, and Dong-Wook Kim

Appl. Phys. Lett. 100, 022901 (2012); http://dx.doi.org/10.1063/1.3675630 (4 pages) | Cited 3 times

Online Publication Date: 9 January 2012

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We investigated the surface potential of TiO2 single crystals using scanning probe microscopy (SPM) under different gas environment. The SPM tip-induced electrical stress resulted in reversal in the surface potential, Vsurf, polarity only in H2/Ar (ΔVsurf = 0.30 eV) and not in Ar and O2. Quantitative measurement of the influence of ambient gas on the surface potential led us to develop a model where the adsorbed oxygen molecules and oxygen vacancies interact to change their relative concentration leading to different surface potential in TiO2. These results will give us insights into ambient-dependent physical phenomena in oxide thin film nanostructures.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
61.46.-w Structure of nanoscale materials
68.55.-a Thin film structure and morphology
68.60.-p Physical properties of thin films, nonelectronic
61.72.jd Vacancies

Ferroelectric phase transition in strained multiferroic (Bi0.9La0.1)2NiMnO6 thin films

E. Langenberg, I. Fina, P. Gemeiner, B. Dkhil, L. Fàbrega, M. Varela, and J. Fontcuberta

Appl. Phys. Lett. 100, 022902 (2012); http://dx.doi.org/10.1063/1.3675869 (3 pages) | Cited 1 time

Online Publication Date: 9 January 2012

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We report here temperature-dependent x-ray structural and Raman spectroscopy data, on the ferromagnetic double-perovskite (Bi0.9La0.1)2NiMnO6 epitaxial thin films. Results indicate a ferroelectric transition occurring at about 450 °C. Low-temperature polarization loops allow to clearly observing polarization switching, thus confirming the multiferroic character of this oxide, and indicate a lower bound of about 6 μC/cm2.
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77.80.B- Phase transitions and Curie point
77.80.Fm Switching phenomena
78.30.Hv Other nonmetallic inorganics

Ultra-wideband surface acoustic wave resonator employing Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 crystals

Jing Chen, Jiansong Liu, Ken-ya Hashimoto, Tatsuya Omori, Changjun Ahn, Xiangyong Zhao, and Haosu Luo

Appl. Phys. Lett. 100, 022903 (2012); http://dx.doi.org/10.1063/1.3675908 (3 pages) | Cited 2 times

Online Publication Date: 9 January 2012

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Theoretical analysis showed that high performance surface acoustic wave (SAW) resonator with an extremely large electromechanical coupling factor K2 could be realized on Y cut X propagating Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (YX-PIN-PMN-PT) substrate. A one-port SAW resonator was designed, fabricated, and characterized on Cu-grating/YX-PIN-PMN-PT substrate structure. The experimental results demonstrate that very large K2 of 57.3% is realizable. Such an extremely large K2 makes PIN-PMN-PT single crystal great potential for realizing wideband SAW filters and tunable SAW filters. The influence of inhomogeneity and instability of the domain structure on the fabricated resonators has been discussed thoroughly for further improvement of the devices.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
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