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27 Oct 2003

Volume 83, Issue 17, pp. 3447-3628

Issue Cover Spotlight Figure

Appl. Phys. Lett. 83, 3453 (2003); http://dx.doi.org/10.1063/1.1622431 (3 pages)

Giacomo Scalari, Stéphane Blaser, Lassaad Ajili, Jérôme Faist, Harvey Beere, Edmund Linfield, David Ritchie, and Giles Davies
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Influence of the doping concentration of Y1−yCayBa2Cu3O7−δ drain-source channels on the properties of superconducting field-effect devices

G. Yu. Logvenov, A. Sawa, C. W. Schneider, and J. Mannhart

Appl. Phys. Lett. 83, 3528 (2003); http://dx.doi.org/10.1063/1.1622780 (3 pages) | Cited 11 times

Online Publication Date: 20 October 2003

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Systematic electric-field-effect studies of the charge transport in doped YBa2Cu3O7−δ films were conducted. For overdoped drain-source channels, the normal-state resistance and the critical temperature Tc decrease with electric-field-induced enhancements of the hole concentration n. For underdoped channels, the resistance decreases, but Tc increases with n. For chemically optimally doped channels, the resistance decreases with n, however, Tc shifts are less pronounced compared with underdoped and overdoped films. The results verify that the superconducting properties of YBa2Cu3O7−δ can be controlled by electric fields, as predicted by the generic phase diagram of the cuprates. © 2003 American Institute of Physics.
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85.25.Qc Superconducting surface acoustic wave devices and other superconducting devices
74.72.-h Cuprate superconductors
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
74.25.Dw Superconductivity phase diagrams

Large room-temperature spin-dependent tunneling magnetoresistance in polycrystalline Fe3O4 films

Hui Liu, E. Y. Jiang, H. L. Bai, R. K. Zheng, H. L. Wei, and X. X. Zhang

Appl. Phys. Lett. 83, 3531 (2003); http://dx.doi.org/10.1063/1.1622440 (3 pages) | Cited 54 times

Online Publication Date: 20 October 2003

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Polycrystalline Fe3O4 films have been prepared by reactive sputtering at room temperature. Transmission electron microscopy images show that the films consist of quite uniform Fe3O4 grains well separated by grain boundaries. It was found that the tunneling of spin-polarized electrons across the antiferromagnetic coupled grain boundaries dominates the transport properties of the films. Magnetoresistance (MR) { = [ρ(H)−ρ(0)]/ρ(0)} shows linear and quadratic magnetic-field dependence in the low-field range when the field is applied parallel and perpendicular to film plane, which is similar to the behaviors observed in the epitaxial Fe3O4 films consisting of a large fraction of antiferromagnetic antiphase domain boundaries. At 300 K, the size of the MR reaches −7.4% under a 50-kOe magnetic field, which is a very large MR for polycrystalline Fe3O4 films. © 2003 American Institute of Physics.
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75.47.Pq Other materials
75.70.Ak Magnetic properties of monolayers and thin films
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.50.Ee Antiferromagnetics
75.47.De Giant magnetoresistance
61.72.Mm Grain and twin boundaries
81.15.Cd Deposition by sputtering
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Spin blockade in ferromagnetic nanocontacts

M. Ye. Zhuravlev, E. Y. Tsymbal, S. S. Jaswal, A. V. Vedyayev, and B. Dieny

Appl. Phys. Lett. 83, 3534 (2003); http://dx.doi.org/10.1063/1.1622986 (3 pages) | Cited 19 times

Online Publication Date: 20 October 2003

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Using a free-electron model and a linear response theory we investigate spin-dependent electronic transport in magnetic nanocontacts in the ballistic regime of conduction. We emphasize the fact that in atomic-size ferromagnetic contacts it is possible to achieve the conductance value of e2/h, which implies a fully spin-polarized electric current. We explore some consequences of this phenomenon. In particular, we show that the presence of a nonmagnetic region in the nanocontact separating two ferromagnetic electrodes can lead to a spin blockade resulting in very large values of magnetoresistance. © 2003 American Institute of Physics.
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73.63.Rt Nanoscale contacts
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.47.-m Magnetotransport phenomena; materials for magnetotransport
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.50.Fq High-field and nonlinear effects
73.23.Ad Ballistic transport
72.25.Mk Spin transport through interfaces
71.15.-m Methods of electronic structure calculations

Large anomalous enhancement of perpendicular exchange bias by introduction of a nonmagnetic spacer between the ferromagnetic and antiferromagnetic layers

F. Garcia, J. Sort, B. Rodmacq, S. Auffret, and B. Dieny

Appl. Phys. Lett. 83, 3537 (2003); http://dx.doi.org/10.1063/1.1619562 (3 pages) | Cited 60 times

Online Publication Date: 20 October 2003

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In (Pt/Co)n/FeMn multilayers, the magnitude of exchange bias, HE, can be considerably enhanced by placing an ultrathin nonmagnetic Pt spacer between the multilayer (ML) and the antiferromagnetic (AFM) layer. The bias is maximum for a spacer layer thickness, t, of a few angstroms and it decreases progressively as t is further increased. This bias enhancement is accompanied by an increase of coercivity, HC. This behavior is due to the role of the Pt spacer in enhancing the perpendicular effective anisotropy of the last Co layer in the ML, which has the effect of increasing the net ferromagnetic (FM)/AFM spin projection, thus leading to the HE and HC enhancements. The decrease of HE and HC for thicker spacer layers is due to the limited range of the FM–AFM proximity effect. © 2003 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Et Exchange and superexchange interactions
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
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