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8 Nov 2010

Volume 97, Issue 19, Articles (19xxxx)

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Appl. Phys. Lett. 97, 193101 (2010); http://dx.doi.org/10.1063/1.3504664 (3 pages)

Qingzhen Hao, Yong Zeng, Xiande Wang, Yanhui Zhao, Bei Wang, I-Kao Chiang, Douglas H. Werner, Vincent Crespi, and Tony Jun Huang
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High-quality epitaxial CoFe/Si(111) heterostructures fabricated by low-temperature molecular beam epitaxy

Y. Maeda, K. Hamaya, S. Yamada, Y. Ando, K. Yamane, and M. Miyao

Appl. Phys. Lett. 97, 192501 (2010); http://dx.doi.org/10.1063/1.3514580 (3 pages) | Cited 4 times

Online Publication Date: 8 November 2010

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We demonstrate atomically controlled heterojunctions consisting of ferromagnetic CoFe alloys and silicon (Si) using low-temperature molecular beam epitaxy with a good atomic matching at the (111) plane. The saturation magnetization of the CoFe layers grown reaches ∼ 85% of the value of bulk samples reported so far, and can be systematically controlled by tuning the ratio of Co to Fe, indicating that the silicidation reactions between CoFe and Si are suppressed and the heterojunctions are very high quality. We find that the Schottky barrier height of the high-quality CoFe/Si(111) junctions is unexpectedly low compared to the previous data for other metal/Si ones, implying the reduction in the Fermi-level-pinning effect. We can expand the available high-quality ferromagnet/Si heterostructures in the field of Si-based spintronics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.at Other materials
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts
72.25.Mk Spin transport through interfaces

Three-dimensional magnetization profile and multiaxes exchange bias in Co antidot arrays

F. Fettar, L. Cagnon, and N. Rougemaille

Appl. Phys. Lett. 97, 192502 (2010); http://dx.doi.org/10.1063/1.3512864 (3 pages) | Cited 1 time

Online Publication Date: 10 November 2010

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Magnetic properties of Cu/Co/Cu trilayers deposited on nanoporous alumina membranes are investigated using a superconducting quantum interference device. Hysteresis loops of the resulting Co antidot arrays show two-step magnetization reversal. Due to oxidation when samples are exposed to air, CoO forms and exchange bias is observed, whether the cooling field is applied within or perpendicular to the surface plane. In the former case, the exchange bias changes sign close to the blocking temperature of Co/CoO. We attribute these effects to the local, crescent shape of the Co films induced by the surface morphology of the membranes, which leads to a three-dimensional magnetization distribution.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Cc Other ferromagnetic metals and alloys
75.30.Et Exchange and superexchange interactions
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Effects of lattice strains on the interfacial potential in La0.67Ca0.33MnO3/SrTiO3:Nb heterojunctions

D. J. Wang, J. R. Sun, Y. W. Xie, Y. B. Li, L. G. Zhang, R. W. Wang, and B. G. Shen

Appl. Phys. Lett. 97, 192503 (2010); http://dx.doi.org/10.1063/1.3515905 (3 pages) | Cited 1 time

Online Publication Date: 10 November 2010

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Oxide p-n heterojunctions composed of La0.67Ca0.33MnO3 (LCMO) films with different thickness and SrTiO3:Nb 0.1 wt % are fabricated and the effects of thickness on the interfacial potential are experimentally studied. Excellent rectifying behavior of the junctions well described by the Shockley equation is observed and the interfacial potential eVD is obtained for all of the junctions based on an analysis of the current-voltage characteristics. The remarkable result of the present work is the strong dependence of the interfacial potential on the thickness of LCMO films: eVD increases from 0.5 to 0.72 eV as the thickness increase from 3.6 to 33 nm. The strain in the LCMO film, which affects the carrier density through modulating the Jahn–Teller effect, is believed to be responsible for the observation.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
68.55.jd Thickness
81.07.Bc Nanocrystalline materials
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
72.20.-i Conductivity phenomena in semiconductors and insulators

Atomistic spin model simulation of magnetic reversal modes near the Curie point

J. Barker, R. F. L. Evans, R. W. Chantrell, D. Hinzke, and U. Nowak

Appl. Phys. Lett. 97, 192504 (2010); http://dx.doi.org/10.1063/1.3515928 (3 pages) | Cited 2 times

Online Publication Date: 10 November 2010

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The so-called linear reversal mode is demonstrated in spin model simulations of the high anisotropy material L10 FePt. Reversal of the magnetization is found to readily occur in the linear regime despite an energy barrier (KV/kBT) that would conventionally ensure stability on this timescale. The timescale for the reversal is also established with a comparison to the Landau–Lifshitz–Bloch equation showing good agreement.
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75.60.Jk Magnetization reversal mechanisms
75.10.Jm Quantized spin models, including quantum spin frustration
75.10.Dg Crystal-field theory and spin Hamiltonians
75.30.Gw Magnetic anisotropy
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Bb Fe and its alloys

On-chip superconductivity via gallium overdoping of silicon

R. Skrotzki, J. Fiedler, T. Herrmannsdörfer, V. Heera, M. Voelskow, A. Mücklich, B. Schmidt, W. Skorupa, G. Gobsch, M. Helm, and J. Wosnitza

Appl. Phys. Lett. 97, 192505 (2010); http://dx.doi.org/10.1063/1.3509411 (3 pages) | Cited 2 times

Online Publication Date: 11 November 2010

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We report on superconducting properties of gallium-enriched silicon layers in commercial (100) oriented silicon wafers. Ion implantation and subsequent rapid thermal annealing have been applied for realizing gallium precipitation beneath a silicon-dioxide cover layer. Depending on the preparation parameters, we observe a sharp drop to zero resistance at 7 K. The critical-field anisotropy proofs the thin-film character of superconductivity. In addition, out-of-plane critical fields of above 9 T and critical current densities exceeding 2 kA/cm2 promote these structures to be possible playgrounds for future microelectronic technology.
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74.25.Sv Critical currents
81.30.Mh Solid-phase precipitation
61.72.Cc Kinetics of defect formation and annealing
61.80.Jh Ion radiation effects
61.72.U- Doping and impurity implantation
74.25.Op Mixed states, critical fields, and surface sheaths

Experimental determination of the magnetization dependent part of the demagnetizing field in hard magnetic materials

A. N. Dobrynin, T. R. Gao, N. M. Dempsey, and D. Givord

Appl. Phys. Lett. 97, 192506 (2010); http://dx.doi.org/10.1063/1.3514554 (3 pages) | Cited 2 times

Online Publication Date: 12 November 2010

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A method for extracting the magnetization dependent part of the demagnetizing field from minor hysteresis loops is described. It applies to hard magnetic materials with irreversible magnetization switching. The method’s validity is tested on the simulated magnetization curves of an assembly of hard magnetic grains, as well as on a thin NdFeB film with out of plane magnetization. Effective demagnetization factors are extracted from the analysis. These factors are smaller than the usually applied sample shape dependent demagnetizing factors.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Ww Permanent magnets
75.70.Ak Magnetic properties of monolayers and thin films

Control of gigahertz permeability and permittivity dispersion by means of nanocrystallization in FeCo based nanocrystalline alloy

Mangui Han, Haipeng Lu, and Longjiang Deng

Appl. Phys. Lett. 97, 192507 (2010); http://dx.doi.org/10.1063/1.3514557 (3 pages) | Cited 1 time

Online Publication Date: 12 November 2010

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An amorphous (FeCo) based alloy has been prepared by a rapid quench method. Subsequent annealing on the amorphous samples gives rise to the coexistence of two magnetic phases: amorphous matrix and nanocrystalline grains (α′-FeCo) with an average size of 9.8 nm. Permeability dispersion behaviors have been studied by Kittel theory [ C. Kittel, J. Phys. Radium 12, 332 (1951)] . The results show that these two magnetic phases contribute to the permeability dispersion. The Cole-Cole dispersion law [ K. S. Cole and R. H. Cole, J. Chem. Phys. 9, 341 (1941)] has been employed to explain the permittivity dispersion within microwave region based on the assumption that multiple dielectric relaxation processes existing. Our results indicate the possibility of tuning the high frequency permeability and permittivity values of (FeCo) based alloy by controlling the magnetic microstructure, which suggests an alternative method to develop smart electromagnetic materials.
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81.16.-c Methods of micro- and nanofabrication and processing
81.40.Gh Other heat and thermomechanical treatments
75.50.Kj Amorphous and quasicrystalline magnetic materials
77.22.Gm Dielectric loss and relaxation
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
77.22.Ch Permittivity (dielectric function)
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