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27 Dec 2010

Volume 97, Issue 26, Articles (26xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 97, 263701 (2010); http://dx.doi.org/10.1063/1.3530124 (3 pages)

Shu-Hsien Liao, Kai-Wen Huang, Hong-Chang Yang, Chang-Te Yen, M. J. Chen, Hsin-Hsien Chen, Herng-Er Horng, and Shieh Yueh Yang
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Influence of Ti on the formation and stability of gas-phase Mg nanoparticles

Gopi Krishnan, G. Palasantzas, and B. J. Kooi

Appl. Phys. Lett. 97, 261912 (2010); http://dx.doi.org/10.1063/1.3533812 (3 pages)

Online Publication Date: 30 December 2010

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The effect of titanium on magnesium nanoparticle formation is investigated in relation to the importance of Mg in hydrogen storage. Addition of Ti reduces the Mg-nanoparticle sizes in the range of 5–20 nm and leads to less protective Mg-oxide shells. This in return accelerates the evaporation of Mg that leads to hollow Mg cores. The presence of oxygen plays a dual role in forming MgO protected stable Mg nanoparticles above a critical size ( ∼ 15 nm) and hollow ones below this size both due to evaporation and oxidation associated Kirkendall effects.
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81.16.-c Methods of micro- and nanofabrication and processing
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
66.30.Ny Chemical interdiffusion; diffusion barriers
88.30.R- Hydrogen storage
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Single-electron transfer between two donors in nanoscale thin silicon-on-insulator field-effect transistors

Earfan Hamid, Daniel Moraru, Juli Cha Tarido, Sakito Miki, Takeshi Mizuno, and Michiharu Tabe

Appl. Phys. Lett. 97, 262101 (2010); http://dx.doi.org/10.1063/1.3530442 (3 pages) | Cited 2 times

Online Publication Date: 28 December 2010

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We describe single-electron transfer between two donors in thin silicon-on-insulator field-effect transistors with phosphorus-doped channel. At low temperatures, single-electron tunneling through one donor can be identified in source-drain current/gate voltage measurements as a single current peak. On this peak, we observed hysteresis most likely as a signature of single-electron transfer with another donor. The origin of single-electron transfer is related to different intensities of coupling between each donor and the interface, as evidenced from simulations. It was found that donor-interface coupling is essential for the energetic transfer of a single-electron location within the two-donor system.
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85.30.Tv Field effect devices
85.35.-p Nanoelectronic devices

Current-driven domain wall motion across a wide temperature range in a (Ga,Mn)(As,P) device

K. Y. Wang, K. W. Edmonds, A. C. Irvine, G. Tatara, E. De Ranieri, J. Wunderlich, K. Olejnik, A. W. Rushforth, R. P. Campion, D. A. Williams, C. T. Foxon, and B. L. Gallagher

Appl. Phys. Lett. 97, 262102 (2010); http://dx.doi.org/10.1063/1.3532095 (3 pages) | Cited 3 times

Online Publication Date: 28 December 2010

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Current-driven magnetic domain wall motion is demonstrated in the quaternary ferromagnetic semiconductor (Ga,Mn)(As,P) at temperatures well below the ferromagnetic transition temperature, with critical currents of the order 105 A cm−2. This is enabled by a much weaker domain wall pinning compared to (Ga,Mn)As layers grown on a strain-relaxed buffer layer. The critical current is shown to be comparable with theoretical predictions. The wide temperature range over which domain wall motion can be achieved indicates that this is a promising system for developing an improved understanding of spin-transfer torque in systems with strong spin-orbit interaction.
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85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
75.76.+j Spin transport effects
75.25.Dk Orbital, charge, and other orders, including coupling of these orders

Interface roughness scattering in laterally coupled InGaAs quantum wires

Vas. P. Kunets, M. D. Teodoro, V. G. Dorogan, P. M. Lytvyn, G. G. Tarasov, R. Sleezer, M. E. Ware, Yu. I. Mazur, J. S. Krasinski, and G. J. Salamo

Appl. Phys. Lett. 97, 262103 (2010); http://dx.doi.org/10.1063/1.3532098 (3 pages) | Cited 1 time

Online Publication Date: 28 December 2010

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Conductivity of In0.38Ga0.62As quantum wires grown on the (311)A plane of GaAs was studied using temperature dependent Hall effect. Detailed analysis of the scattering phenomena which control electron mobility along the wires indicates that the most significant scattering mechanism which limits electron mobility at low temperatures is scattering from interface roughness. This finding contributes to the general understanding of the potential to use self-assembled semiconductor quantum wires in the fabrication of thermoelectric devices where one-dimensionality and enhanced scattering at rough boundaries are important.
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68.35.Ct Interface structure and roughness
73.21.Hb Quantum wires
72.20.Fr Low-field transport and mobility; piezoresistance
72.20.My Galvanomagnetic and other magnetotransport effects
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Coherent heteroepitaxy of Bi2Se3 on GaAs (111)B

A. Richardella, D. M. Zhang, J. S. Lee, A. Koser, D. W. Rench, A. L. Yeats, B. B. Buckley, D. D. Awschalom, and N. Samarth

Appl. Phys. Lett. 97, 262104 (2010); http://dx.doi.org/10.1063/1.3532845 (3 pages) | Cited 10 times

Online Publication Date: 28 December 2010

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We report the heteroepitaxy of single crystal thin films of Bi2Se3 on the (111)B surface of GaAs by molecular beam epitaxy. We find that Bi2Se3 grows highly c-axis oriented, with an atomically sharp interface with the GaAs substrate. By optimizing the growth of a very thin GaAs buffer layer before growing the Bi2Se3, we demonstrate the growth of thin films with atomically flat terraces over hundreds of nanometers. Initial time-resolved Kerr rotation measurements herald opportunities for probing coherent spin dynamics at the interface between a candidate topological insulator and a large class of GaAs-based heterostructures.
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81.05.Hd Other semiconductors
78.20.Ls Magneto-optical effects
78.20.Ek Optical activity
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.ag Semiconductors
78.66.Li Other semiconductors

Ambipolar bistable switching effect of graphene

Young Jun Shin, Jae Hyun Kwon, Gopinadhan Kalon, Kai-Tak Lam, Charanjit S. Bhatia, Gengchiau Liang, and Hyunsoo Yang

Appl. Phys. Lett. 97, 262105 (2010); http://dx.doi.org/10.1063/1.3532849 (3 pages) | Cited 7 times

Online Publication Date: 28 December 2010

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Reproducible current hysteresis is observed in graphene with a back gate structure in a two-terminal configuration. An opposite sequence of switching with different charge carriers, holes, and electrons is found. The charging and discharging effect is proposed to explain this ambipolar bistable hysteretic switching. To confirm this hypothesis, one-level transport model simulations including charging effect are performed and the results are consistent with our experimental data. Methods of improving the on/off ratio of graphene resistive switching are suggested.
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85.30.Tv Field effect devices
85.75.Hh Spin polarized field effect transistors

Increased critical thickness for high Ge-content strained SiGe-on-Si using selective epitaxial growth

Meekyung Kim, Pouya Hashemi, and Judy L. Hoyt

Appl. Phys. Lett. 97, 262106 (2010); http://dx.doi.org/10.1063/1.3530433 (3 pages)

Online Publication Date: 28 December 2010

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The onset of misfit dislocation formation, i.e., the critical thickness for heteroepitaxy, is studied for selective epitaxial growth of high Ge-content, strained SiGe on oxide-patterned Si wafers. Misfit dislocation spacing was analyzed as a function of film thickness using plan-view transmission-electron microscopy. For selective epitaxial growth at 450 °C, the critical thickness for Si0.33Ge0.67 is found to be 8.5 nm. This is a twofold increase compared to the 4.0 nm theoretical equilibrium critical thickness and the 4.5 nm critical thickness measured for growth on bare Si wafers. The misfit dislocation density for selective epitaxial growth is strongly influenced by the shape and orientation of the growth area.
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81.05.Hd Other semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Enhanced Ohmic contact via graphitization of polycrystalline silicon carbide

F. Liu, B. Hsia, C. Carraro, A. P. Pisano, and R. Maboudian

Appl. Phys. Lett. 97, 262107 (2010); http://dx.doi.org/10.1063/1.3531552 (3 pages)

Online Publication Date: 28 December 2010

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Electrical contact to silicon carbide with low contact resistivity and high stability is a critical requirement for SiC-based microsystem and nanosystem technology for harsh environment applications. In this letter, nanocrystalline graphitic carbon is grown at the interface between SiC and Pt to lower the Ohmic contact resistivity and enhance the stability of Pt contacts to polycrystalline 3C-SiC operated at elevated temperatures. Analysis shows that reduced barrier height, oxide-free surface, reduced density of vacancy defects, and suppressed reactivity between Pt and SiC are likely responsible for the reduced Ohmic contact resistivity and high thermal stability of Pt contacts to graphitized SiC.
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73.40.Cg Contact resistance, contact potential
61.72.jd Vacancies
73.40.Ns Metal-nonmetal contacts

Room temperature coherent and voltage tunable terahertz emission from nanometer-sized field effect transistors

S. Boubanga-Tombet, F. Teppe, J. Torres, A. El Moutaouakil, D. Coquillat, N. Dyakonova, C. Consejo, P. Arcade, P. Nouvel, H. Marinchio, T. Laurent, C. Palermo, A. Penarier, T. Otsuji, L. Varani, et al.

Appl. Phys. Lett. 97, 262108 (2010); http://dx.doi.org/10.1063/1.3529464 (3 pages) | Cited 1 time

Online Publication Date: 28 December 2010

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We report on reflective electro-optic sampling measurements of terahertz emission from nanometer-gate-length InGaAs-based high electron mobility transistors. The room temperature coherent gate-voltage tunable emission is demonstrated. We establish that the physical mechanism of the coherent terahertz emission is related to the plasma waves driven by simultaneous current and optical excitation. A significant shift of the plasma frequency and the narrowing of the emission with increasing channel’s current are observed and explained as due to the increase in the carriers’ density and drift velocity.
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85.30.Tv Field effect devices
84.40.Lj Microwave integrated electronics
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Electron spin dynamics in heavily Mn-doped (Ga,Mn)As

Yonggang Zhu, Lifen Han, Lin Chen, Xinhui Zhang, and Jianhua Zhao

Appl. Phys. Lett. 97, 262109 (2010); http://dx.doi.org/10.1063/1.3531754 (3 pages) | Cited 1 time

Online Publication Date: 29 December 2010

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Electron spin relaxation and related mechanisms in heavily Mn-doped (Ga,Mn)As are studied by performing time-resolved magneto-optical Kerr effect measurements. At low temperature, s-d exchange scattering dominates electron spin relaxation, whereas the Bir–Aronov–Pikus mechanism and Mn impurity scattering play important roles at high temperature. The temperature-dependent spin relaxation time exhibits an anomaly around the Curie temperature (Tc) that implies that thermal fluctuation is suppressed by short-range correlated spin fluctuation above Tc.
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78.20.Ls Magneto-optical effects
78.66.Nk Insulators
76.30.-v Electron paramagnetic resonance and relaxation
75.70.Ak Magnetic properties of monolayers and thin films

Single electron pumping through a quantum dot-embedded carbon nanotube using surface acoustic wave

Bum-Kyu Kim, Ju-Jin Kim, Minky Seo, Yunchul Chung, Byung Chil Woo, Jinhee Kim, Woon Song, and Nam Kim

Appl. Phys. Lett. 97, 262110 (2010); http://dx.doi.org/10.1063/1.3532852 (3 pages)

Online Publication Date: 29 December 2010

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We have studied acoustoelectric current through a quantum dot-embedded carbon nanotube induced by a surface acoustic wave. The measurements were carried out on a same device but in two very different quantum dot charging energy Ec regimes ( ∼ 50 and ∼ 5 meV). The results showed dramatic differences in induced acoustoelectric current depending on Ec. The induced acoustoelectric current showed a polarity reversal around the Coulomb blockade peak when Ec is small (5 meV). For a large Ec (50 meV), however, a current plateau was observed as a function of surface acoustic wave powers as well as gate voltages.
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85.35.Kt Nanotube devices
85.35.Gv Single electron devices
85.35.Ds Quantum interference devices

Surface roughness scattering in two dimensional electron gas channel

B. Liu, Y. W. Lu, G. R. Jin, Y. Zhao, X. L. Wang, Q. S. Zhu, and Z. G. Wang

Appl. Phys. Lett. 97, 262111 (2010); http://dx.doi.org/10.1063/1.3532967 (3 pages) | Cited 6 times

Online Publication Date: 29 December 2010

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The mobility of AlxGa1−xN/GaN heterostructure two dimensional electron gas channel limited by surface roughness scattering was calculated considering the strong spontaneous and piezoelectric polarizations in III-group nitride heterostructure. The electronic mobility on the order of 104–105 cm2 V−1 s−1 was estimated. We found that the mobility limited by surface roughness scattering is very sensitive to barrier layer thickness fluctuation.
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81.05.Ea III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.25.+i Surface conductivity and carrier phenomena
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)

Anticrosstalk characteristics correlated with the set process for α-Fe2O3/Nb–SrTiO3 stack-based resistive switching device

Y. S. Chen, B. Chen, B. Gao, F. F. Zhang, Y. J. Qiu, G. J. Lian, L. F. Liu, X. Y. Liu, R. Q. Han, and J. F. Kang

Appl. Phys. Lett. 97, 262112 (2010); http://dx.doi.org/10.1063/1.3532970 (3 pages) | Cited 4 times

Online Publication Date: 29 December 2010

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A resistive switching device based on the stacked α-Fe2O3/Nb–SrTiO3 is proposed and fabricated that demonstrates excellent bipolar resistive switching behaviors including the uniformity, endurance, and retention performance. The Schottky-like current-voltage characteristics correlated with set process were observed in both high resistive states (HRSs) and low resistive states (LRSs) of the device. Importantly, the anticrosstalk characteristic, possessing higher reversed-biased LRS resistance than the forwarded-biased HRS resistance, indicates the potential applications of the stacked α-Fe2O3/Nb–SrTiO3 for multilevel storage in the cross-bar memory arrays. The carrier injection and trapping mechanism is suggested to explain the observed phenomena.
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84.30.Sk Pulse and digital circuits

A graphene quantum dot with a single electron transistor as an integrated charge sensor

Lin-Jun Wang, Gang Cao, Tao Tu, Hai-Ou Li, Cheng Zhou, Xiao-Jie Hao, Zhan Su, Guang-Can Guo, Hong-Wen Jiang, and Guo-Ping Guo

Appl. Phys. Lett. 97, 262113 (2010); http://dx.doi.org/10.1063/1.3533021 (3 pages) | Cited 5 times

Online Publication Date: 29 December 2010

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A quantum dot (QD) with an integrated charge sensor is becoming a common architecture for a spin or charge based solid state qubit. To implement such a structure in graphene, we have fabricated a twin-dot structure in which the larger dot serves as a single electron transistor (SET) to read out the charge state of the nearby gate controlled small QD. A high SET sensitivity of 10−3e/math allowed us to probe Coulomb charging as well as excited state spectra of the QD, even in the regime where the current through the QD is too small to be measured by conventional transport means.
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85.35.Gv Single electron devices
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Molecular conductivity switching of two benzene rings under electric field

M. G. Vergniory, J. M. Granadino-Roldan, A. Garcia-Lekue, and Lin-Wang Wang

Appl. Phys. Lett. 97, 262114 (2010); http://dx.doi.org/10.1063/1.3533383 (3 pages)

Online Publication Date: 29 December 2010

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A molecular transistor based on torsion-angle conformation change driven by gate electric field is designed and studied using ab initio calculations. This transistor consists of a SH–C6H2F(CH3)C6H2(CH3)F–SH molecule sandwiched between two Au(111) electrodes, where the interaction between the molecular dipole and a gate voltage induced electric field will cause the molecule to twist along its c-axis, changing the quantum conductivity of the molecule. The effect of thermal fluctuation on the molecular conformation is studied, so is the ability of the transistor to shut off its current. The advantages and challenges of using such molecular conformation change as a mechanism for transistor gating are discussed.
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85.65.+h Molecular electronic devices

Electron-phonon coupling in single-walled carbon nanotubes determined by shot noise

F. Wu, P. Virtanen, S. Andresen, B. Plaçais, and P. J. Hakonen

Appl. Phys. Lett. 97, 262115 (2010); http://dx.doi.org/10.1063/1.3533018 (3 pages)

Online Publication Date: 29 December 2010

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We have measured shot noise in metallic single-walled carbon nanotubes of length L = 1 μm and have found strong suppression of noise with increasing voltage. We conclude that the coupling of electron and phonon baths at temperatures Te and Tph is described at intermediate bias (20 mV<Vds≲200 mV) by heat flow equation P = ΣL(Te3−Tph3), where Σ ∼ 3×10−9 W/m K3 due to electron interaction with acoustic phonons, while at higher voltages optical phonon-electron interaction leads to P = κopL[N(Te)−N(Tph)], where N(T) = 1/[exp(ℏΩ/kBT)−1] with optical phonon energy ℏΩ and κop = 2×102 W/m.
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71.38.-k Polarons and electron-phonon interactions
72.70.+m Noise processes and phenomena
63.20.kd Phonon-electron interactions

Isolation blocking voltage of nitrogen ion-implanted AlGaN/GaN high electron mobility transistor structure

C. F. Lo, T. S. Kang, L. Liu, C. Y. Chang, S. J. Pearton, I. I. Kravchenko, O. Laboutin, J. W. Johnson, and F. Ren

Appl. Phys. Lett. 97, 262116 (2010); http://dx.doi.org/10.1063/1.3533381 (3 pages) | Cited 9 times

Online Publication Date: 30 December 2010

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Nitrogen ion-implanted AlGaN/GaN high electron mobility transistor structures showed an isolation blocking voltage of 900 V with a leakage current at 1 μA/mm across an implanted isolation-gap of 10 μm between two Ohmic pads. The effect of implanted gap distance (1.7, 5, or 10 μm) between two Ohmic contact pads was evaluated. The isolation current density was determined to be solely dependent on the applied field between the contact pads. A model using a combination of resistive current and Poole–Frenkel current is consistent with the experimental data. The resistance of the isolation implantation region significantly decreased after the sample was annealed at temperatures above 600 °C.
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85.30.Tv Field effect devices

Electronic conduction in amorphous and polycrystalline zinc-indium oxide films

Vladimir L. Kuznetsov, David H. O’Neil, Michael Pepper, and Peter P. Edwards

Appl. Phys. Lett. 97, 262117 (2010); http://dx.doi.org/10.1063/1.3533382 (3 pages) | Cited 2 times

Online Publication Date: 30 December 2010

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We report on the electronic properties of both amorphous and polycrystalline zinc-indium oxide thin films with similar degenerate electron concentrations just above the insulator-to-metal transition. The highest electron mobilities occur in amorphous oxide films deposited at 100 °C; for these, structural disorder is on a spatial scale much smaller than the characteristic electron wavelength ( ∼ 3 nm) of the conduction electron gas. For polycrystalline films fabricated at 200–300 °C enhanced electron scattering occurs at evolving grain boundaries when the grain size is comparable to the electron wavelength. Larger, highly crystalline grains form for deposition at 500 °C with concomitant higher carrier mobilities.
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73.61.Ng Insulators
68.55.aj Insulators
73.50.Dn Low-field transport and mobility; piezoresistance
72.20.Fr Low-field transport and mobility; piezoresistance
81.15.Fg Pulsed laser ablation deposition
61.72.Mm Grain and twin boundaries

Peculiarities of impact ionization of Impurity Al in SiC polytypes

V. I. Sankin, A. M. Monakhov, P. P. Shkrebiy, P. L. Abramov, N. I. Sablina, and N. S. Averkiev

Appl. Phys. Lett. 97, 262118 (2010); http://dx.doi.org/10.1063/1.3527964 (3 pages)

Online Publication Date: 30 December 2010

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The specific character of impact ionization of a small radius impurities was investigated in polytypes 6H-, 4H-, and 15R-SiC. The I-V characteristics of Al breakdown in 6H-, 4H-, and 15R-SiC in electrical field were studied. It was shown that at 77 K the impurity breakdown takes place only under the large impurity concentrations (three orders larger than that in Ge). The following data were obtained: the decreasing dependence of breakdown field due to the concentration increase, the absence of the low temperature breakdown at low impurity concentration, and gigantic enhancement of breakdown field when the field is parallel to the crystal axis.
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72.20.Ht High-field and nonlinear effects
71.70.Ch Crystal and ligand fields
72.80.Jc Other crystalline inorganic semiconductors
77.22.Jp Dielectric breakdown and space-charge effects
61.50.Ks Crystallographic aspects of phase transformations; pressure effects

Ambipolar diffusion of photoexcited carriers in bulk GaAs

Brian A. Ruzicka, Lalani K. Werake, Hassana Samassekou, and Hui Zhao

Appl. Phys. Lett. 97, 262119 (2010); http://dx.doi.org/10.1063/1.3533664 (3 pages) | Cited 2 times

Online Publication Date: 30 December 2010

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The ambipolar diffusion of carriers in bulk GaAs is studied by using an ultrafast pump-probe technique with a high spatial resolution. Carriers with a pointlike spatial profile are excited by a tightly focused pump laser pulse. The spatiotemporal dynamics of the carriers are monitored by a time-delayed and spatially scanned probe pulse. Ambipolar diffusion coefficients are deduced from linear fits to the expansion of the area of the profiles, and are found to decrease from about 170 cm2 s−1 at 10 K to about 20 cm2 s−1 at room temperature. Our results are consistent with those deduced from previously measured mobilities.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Ey III-V and II-VI semiconductors
05.45.-a Nonlinear dynamics and chaos
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Magnetoresistance in a lithography defined single constrained domain wall spin-valve

Yudong Wang, C. H. de Groot, D. Claudio-Gonzalez, and Hans Fangohr

Appl. Phys. Lett. 97, 262501 (2010); http://dx.doi.org/10.1063/1.3531666 (3 pages) | Cited 2 times

Online Publication Date: 28 December 2010

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We have measured domain wall magnetoresistance in a single lithographically constrained domain wall. An H-shaped Ni nanobridge was fabricated by e-beam lithography with the two sides being single magnetic domains showing independent magnetic switching. The connection between the sides constrains the domain wall when the sides line up antiparallel. The magnetoresistance curve clearly identifies the magnetic configurations that are expected from a spin-valvelike structure. The value of the magnetoresistance at room temperature is around 0.1% or 0.4 Ω. This value is shown to be in agreement with a theoretical formulation based on spin accumulation. Micromagnetic simulations show that it is possible to reduce the size of the domain wall further by shortening the length of the bridge.
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72.15.Gd Galvanomagnetic and other magnetotransport effects
81.16.Nd Micro- and nanolithography
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.46.-w Structure of nanoscale materials
75.60.Ch Domain walls and domain structure

Spin-transfer pulse switching: From the dynamic to the thermally activated regime

D. Bedau, H. Liu, J. Z. Sun, J. A. Katine, E. E. Fullerton, S. Mangin, and A. D. Kent

Appl. Phys. Lett. 97, 262502 (2010); http://dx.doi.org/10.1063/1.3532960 (3 pages) | Cited 11 times

Online Publication Date: 30 December 2010

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The effect of thermal fluctuations on spin-transfer switching has been studied for a broad range of time scales (subnanoseconds to seconds) in a model system, a uniaxial thin film nanomagnet. The nanomagnet is incorporated into a spin-valve nanopillar, which is subject to spin-polarized current pulses of variable amplitude and duration. Two physical regimes are clearly distinguished: a long pulse duration regime, in which reversal occurs by spin-transfer assisted thermal activation over an energy barrier, and a short-time large pulse amplitude regime, in which the switching probability is determined by the spin-angular momentum in the current pulse.
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72.25.-b Spin polarized transport
75.75.-c Magnetic properties of nanostructures
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Impact of edge-barrier pinning in superconducting thin films

W. A. Jones, P. N. Barnes, M. J. Mullins, F. J. Baca, R. L. S. Emergo, J. Wu, T. J. Haugan, and J. R. Clem

Appl. Phys. Lett. 97, 262503 (2010); http://dx.doi.org/10.1063/1.3529945 (3 pages)

Online Publication Date: 30 December 2010

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It has been suggested that edge-barrier pinning might cause the critical current density (Jc) in bridged superconducting films to increase. Subsequent work indicated that this edge-barrier effect does not impact bridges larger than 1 μm. However, we provide a theoretical assessment with supporting experimental data suggesting edge-barrier pinning can significantly enhance Jc for bridges of a few microns or even tens of microns thus skewing any comparisons among institutions. As such, when reporting flux pinning and superconductor processing improvements for Jc comparisons, the width of the sample has to be taken into consideration as is currently done with film thickness.
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74.78.-w Superconducting films and low-dimensional structures
74.25.Sv Critical currents
74.25.Wx Vortex pinning (includes mechanisms and flux creep)

Longitudinal spin-Seebeck effect in sintered polycrystalline (Mn,Zn)Fe2O4

Ken-ichi Uchida, Tatsumi Nonaka, Takeru Ota, and Eiji Saitoh

Appl. Phys. Lett. 97, 262504 (2010); http://dx.doi.org/10.1063/1.3533397 (3 pages) | Cited 6 times

Online Publication Date: 30 December 2010

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This paper reports that the longitudinal spin-Seebeck effect appears even in a sintered polycrystalline Mn-Zn ferrite [(Mn,Zn)Fe2O4] slab. The effect drives a spin current flowing across an interface between the (Mn,Zn)Fe2O4 slab and an attached Pt film along a temperature gradient and it generates electric voltage via the inverse spin-Hall effect in the Pt film. Since the observed phenomenon enables thermal generation of electric voltage from commonly used polycrystalline insulators, it can be used as a versatile and low-cost thermoelectric generator.
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72.20.Pa Thermoelectric and thermomagnetic effects
73.40.Ns Metal-nonmetal contacts
72.20.My Galvanomagnetic and other magnetotransport effects
75.50.Gg Ferrimagnetics

Ab initio studies of the effect of nanoclusters on magnetostriction of Fe1−xGax alloys

Hui Wang, Y. N. Zhang, Teng Yang, Z. D. Zhang, L. Z. Sun, and R. Q. Wu

Appl. Phys. Lett. 97, 262505 (2010); http://dx.doi.org/10.1063/1.3533659 (3 pages) | Cited 1 time

Online Publication Date: 30 December 2010

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Using the density functional calculations, we investigated the effect of nanoprecipitation on the magnetostriction of Fe1−xGax alloys. While the B2-like FeGa clusters undergo slight tetragonal distortion, D03-like FeGa clusters remain cubic in the Fe matrix. Moreover, we found that B2-like nanostructures produce negative magnetostriction, whereas D03-like nanostructures give small positive magnetostriction in the hypothetical inhomogeneous structures. Therefore, the formation of nanoscale precipitates cannot be the reason for the extraordinary enhancement of magnetostriction of Fe1−xGax alloys.
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75.80.+q Magnetomechanical effects, magnetostriction
75.50.Bb Fe and its alloys
81.30.Mh Solid-phase precipitation
75.50.Tt Fine-particle systems; nanocrystalline materials
75.75.-c Magnetic properties of nanostructures
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