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8 Nov 2004

Volume 85, Issue 19, pp. 4269-4539

Issue Cover Spotlight Figure

Appl. Phys. Lett. 85, 4343 (2004); http://dx.doi.org/10.1063/1.1814814 (3 pages)

H. Isshiki, M. J. A. de Dood, A. Polman, and T. Kimura
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Tailoring of ferromagnetic Pr0.85Ca0.15MnO3∕ferroelectric Ba0.6Sr0.4TiO3 superlattices for multiferroic properties

P. Murugavel, D. Saurel, W. Prellier, Ch. Simon, and B. Raveau

Appl. Phys. Lett. 85, 4424 (2004); http://dx.doi.org/10.1063/1.1811800 (3 pages) | Cited 31 times

Online Publication Date: 8 November 2004

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Superlattices composed of ferromagnetic Pr0.85Ca0.15MnO3 and ferroelectric Ba0.6Sr0.4TiO3 layers were fabricated on (100) SrTiO3 substrates by a pulsed-laser deposition method. The capacitance and resistive parts of the samples were analyzed from the complex impedance measurements. The superlattice with larger ferroelectric thickness shows unique characteristics which are not present in the parent ferromagnetic thin film. The superlattice shows both ferromagnetic and ferroelectric transitions which is an evidence for the coexistence of both the properties. The high magnetoresistance (40% at 80 K) shown by the superlattice can be attributed to the coupling between ferromagnetic and ferroelectric layers, i.e., to the magnetoelectric effect.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
75.50.Dd Nonmetallic ferromagnetic materials
81.15.Fg Pulsed laser ablation deposition
73.61.Ng Insulators
77.55.-g Dielectric thin films
75.80.+q Magnetomechanical effects, magnetostriction
77.80.B- Phase transitions and Curie point
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
77.22.Ch Permittivity (dielectric function)

High-power-density fault-current limiting devices using superconducting YBa2Cu3O7 films and high-resistivity alloy shunt layers

Hirofumi Yamasaki, Mitsuho Furuse, and Yoshihiko Nakagawa

Appl. Phys. Lett. 85, 4427 (2004); http://dx.doi.org/10.1063/1.1812572 (3 pages) | Cited 21 times

Online Publication Date: 8 November 2004

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Switching of superconducting thin-film resistive fault-current limiting devices with alloy shunt layers was studied. Au–Ag alloy thin films, whose room-temperature resistivity is about six times higher than that of pure gold, were sputter deposited on YBa2Cu3O7 films on sapphire substrates with high critical current density of Jc=3.05±0.05 MA∕cm2. A small sample, 5 mm wide and 40 mm long, had the capacity of a rated current of 32 Arms in normal operation and withstood a high voltage of 107 Vrms for 0.1 s after switching, resulting in a very high switching power density of ∼1.7 kVA∕cm2, which is more than four times higher than conventional devices using gold shunt layers.
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84.32.Ff Conductors, resistors (including thermistors, varistors, and photoresistors)
85.25.Qc Superconducting surface acoustic wave devices and other superconducting devices
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables
74.78.-w Superconducting films and low-dimensional structures
81.15.Cd Deposition by sputtering
74.25.Sv Critical currents

Dynamic stress-induced low-temperature ordering of FePt

Chih-Huang Lai, Cheng-Han Yang, C. C. Chiang, T. Balaji, and T. K. Tseng

Appl. Phys. Lett. 85, 4430 (2004); http://dx.doi.org/10.1063/1.1819985 (3 pages) | Cited 32 times

Online Publication Date: 8 November 2004

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The ordering temperature of FePt was significantly reduced to 275°C by introducing a Cu underlayer on the HF-cleaned Si(001) substrate. A coercivity Hc as high as 6200 Oe can be achieved after postannealing at 275°C, and Hc can be further increased to 7000 Oe after 300°C postannealing. During the formation of copper silicide Cu3Si, the expanded volume induces a dynamic in-plane tensile stress on FePt films, which accelerates the formation of the ordered FePt phase at low temperature. Different from the static stress induced by the lattice mismatch between films and underlayers, the dynamic stress is relaxed after the formation of Cu3Si is completed; therefore, the low-temperature ordering of FePt mainly takes place simultaneously with the evolution of dynamic stress during the formation of Cu3Si. The coercivity of FePt depends on the amount of Cu3Si and on the stress developed by Cu3Si.
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75.50.Bb Fe and its alloys
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.70.Ak Magnetic properties of monolayers and thin films
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.50.Vv High coercivity materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.40.Gh Other heat and thermomechanical treatments
68.60.Bs Mechanical and acoustical properties

Magnetization measurements on Li2Pd3B superconductor

P. Badica, T. Kondo, T. Kudo, Y. Nakamori, S. Orimo, and K. Togano

Appl. Phys. Lett. 85, 4433 (2004); http://dx.doi.org/10.1063/1.1814433 (3 pages) | Cited 11 times

Online Publication Date: 8 November 2004

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Magnetization in dc magnetic fields and at different temperatures has been measured on the antiperovskite Li2Pd3B with a cubic structure composed of distorted Pd6B octahedrons. This material was recently found to exhibit superconductivity at 7–8 K. The critical fields Hc1(0) and Hc2(0) are determined to be 135 Oe and 4 T, respectively. Critical current density, scaling of the pinning force within the Kramer model, and irreversibility field data are presented. Several superconductivity parameters were deduced: Coherence length ξ=9.1 nm, penetration depth λ=194 nm, and Ginzburg–Landau parameter κ=21. The material resembles other boride superconductors from the investigated points of view.
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74.70.Dd Ternary, quaternary, and multinary compounds (including Chevrel phases, borocarbides, etc.)
74.25.Ha Magnetic properties including vortex structures and related phenomena
74.25.Sv Critical currents
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)

Nonlinear microwave response of MgB2

T. Dahm and D. J. Scalapino

Appl. Phys. Lett. 85, 4436 (2004); http://dx.doi.org/10.1063/1.1815067 (3 pages) | Cited 17 times

Online Publication Date: 8 November 2004

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We calculate the intrinsic nonlinear microwave response of the two gap superconductor MgB2 in the clean and dirty limits. Due to the small value of the π-band gap, the nonlinear response at low temperatures is larger than for a single gap Bardeen–Cooper–Schrieffer s-wave superconductor with a transition temperature of 40 K. Comparing this result with the intrinsic nonlinear d-wave response of YBa2Cu3O7, we find a comparable response at temperatures around 20 K. Due to its two gap nature, impurity scattering in MgB2 can be used to reduce the nonlinear response if the scattering rate in the π-band is made larger than the one in the σ-band.
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74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
78.70.Gq Microwave and radio-frequency interactions
74.10.+v Occurrence, potential candidates
74.25.Jb Electronic structure (photoemission, etc.)
74.25.F- Transport properties

Planar magnetoinductive wave transducers: Theory and applications

M. J. Freire, R. Marqués, F. Medina, M. A. G. Laso, and F. Martín

Appl. Phys. Lett. 85, 4439 (2004); http://dx.doi.org/10.1063/1.1814428 (3 pages) | Cited 37 times

Online Publication Date: 8 November 2004

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Transduction of magnetoinductive waves (MIWs) in planar technology is demonstrated. A transducer consisting of a one-dimensional periodic array of metallic split squared ring resonators (SSRR), placed between a pair of microstrip lines on a planar substrate has been fabricated and measured. The microstrip lines are inductively coupled to the SSRRs located at the ends of the periodic array and excite MIWs that propagate along the array. The theoretical model for the dispersion of MIWs is used to predict the dispersion relation and the delay time in the device. The delay time was measured and a good agreement was found with the theoretical predictions. The transmission coefficient of the device was also measured. The theoretical and experimental results suggest that the proposed configuration can find application in the design of delay lines and other microwave devices. In fact, the behavior of the proposed transducer is similar to that of the conventional ferrite magnetostatic-wave transducer. However, ferrite devices are fragile, difficult to integrate, and require a heavy external magnet or electromagnet to magnetize the ferrite to saturation. Since all these drawbacks are not present in the proposed configuration, it may be a useful alternative to those devices for many practical applications.
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84.40.Az Waveguides, transmission lines, striplines
75.30.Ds Spin waves

Band-structure calculations of imperfect Co2MnGe Heusler compounds

M. J. Carey, T. Block, and B. A. Gurney

Appl. Phys. Lett. 85, 4442 (2004); http://dx.doi.org/10.1063/1.1818735 (3 pages) | Cited 11 times

Online Publication Date: 8 November 2004

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The effect of imperfections on the bandstructure of Co2MnGe is explored. In particular, the effect of uniform and tetragonal distortions, and Cu, Al, O, Rh, and Sn impurities on the half-metallic behavior are examined. We find that a high spin polarization can be maintained even under significant strains and distortions. However, we find that impurities with as little as 3% concentration will generally have a significant detrimental effect on the half-metallic behavior of the Heusler alloy.
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71.20.Gj Other metals and alloys
71.15.-m Methods of electronic structure calculations
61.72.S- Impurities in crystals
72.25.Ba Spin polarized transport in metals
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