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1 Nov 2004

Volume 85, Issue 18, pp. 3959-4247

Issue Cover Spotlight Figure

Appl. Phys. Lett. 85, 4142 (2004); http://dx.doi.org/10.1063/1.1811774 (3 pages)

Hong Jin Fan, Roland Scholz, Florian M. Kolb, and Margit Zacharias
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Study of the interaction of 4H–SiC and 6H–SiC(0001)Si surfaces with atomic nitrogen

Maria Losurdo, Maria M. Giangregorio, Giovanni Bruno, April Brown, and Tong-Ho Kim

Appl. Phys. Lett. 85, 4034 (2004); http://dx.doi.org/10.1063/1.1814438 (3 pages) | Cited 9 times

Online Publication Date: 3 November 2004

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The interaction of atomic nitrogen with 4H– and 6H–SiC(0001) Si-face surfaces is investigated. Clean and atomically smooth terraced surfaces obtained by in situ cleaning using atomic hydrogen have been exposed at 200 °C and 750 °C to atomic nitrogen produced by a rf remote N2 plasma. Spectroscopic ellipsometry is used for real-time monitoring of the kinetics of SiC surface modifications, and determining the thickness and properties of the nitrided layer. Surface potential measurements reveal the band bending of the nitrided SiC surface. An improvement in the heteroepitaxy of GaN on the low-temperature nitrided SiC surface is found.
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81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
81.65.Cf Surface cleaning, etching, patterning
68.35.B- Structure of clean surfaces (and surface reconstruction)
79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.05.Hd Other semiconductors

Hydrogen-induced atomic deformation in SrBi2Nb2O9 perovskite structure

Ik Soo Kim, In-Hoon Choi, Yong Tae Kim, Seong-Il Kim, Dong Chul Yoo, and Jeong Yong Lee

Appl. Phys. Lett. 85, 4037 (2004); http://dx.doi.org/10.1063/1.1815064 (3 pages)

Online Publication Date: 3 November 2004

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The origin of hydrogen-induced structural deformation of ferroelectric SrBi2Nb2O9 (SBN) thin films is investigated by annealing in forming gas (3% H2–97% N2). High resolution transmission electron microscopy and fast Fourier transformation analysis reveal that the {115} planes are shifted upward and downward by 0.92 math along {115} plane after forming gas annealing, resulting in (00l) planes inclined by 9.54°. This shifted distance of 0.92 math means that the perovskite structure is distorted by 29.98% compared to the normal interatomic distance of 3.077 math. This distorted perovskite structure results in degradation of ferroelectric properties. However, this lattice deformation and ferroelectric property of SBN films are recovered after annealing in oxygen ambient.
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77.80.Dj Domain structure; hysteresis
81.40.Gh Other heat and thermomechanical treatments
61.66.Fn Inorganic compounds
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
68.37.Lp Transmission electron microscopy (TEM)
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Elliptically polarized pump-probe spectroscopy and its application to observation of electron-spin relaxation in GaAs quantum wells

Tianshu Lai, Luning Liu, Qian Shou, Liang Lei, and Weizhu Lin

Appl. Phys. Lett. 85, 4040 (2004); http://dx.doi.org/10.1063/1.1811794 (3 pages) | Cited 8 times

Online Publication Date: 3 November 2004

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An elliptically polarized pump-probe spectroscopy is developed. A theoretical model is derived from the rate equations of two-level system with small signal approximation to describe the experimental signal of the spectroscopy. The spectroscopy eliminates the systematic errors between theories and experimental results in present circularly polarized pump-probe spectroscopy, and is implemented easily in experiments. The initial degree of spin polarization of carriers in an excited state can be extracted by means of the spectroscopy, which is an important parameter in the investigation of spatial transport of spin polarization. The electron-spin relaxation in GaAs quantum wells is studied by using this spectroscopy.
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73.63.Hs Quantum wells
72.25.Dc Spin polarized transport in semiconductors

Extremely high electron mobility of pseudomorphic In0.74Ga0.26As∕In0.46Al0.54As modulation-doped quantum wells grown on (411)A InP substrates by molecular-beam epitaxy

T. Kitada, T. Aoki, I. Watanabe, S. Shimomura, and S. Hiyamizu

Appl. Phys. Lett. 85, 4043 (2004); http://dx.doi.org/10.1063/1.1807023 (3 pages) | Cited 4 times

Online Publication Date: 3 November 2004

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Much enhanced electron mobility of 105 000 cm2∕V s with a high sheet electron concentration (Ns) of 3.1×1012 cm−12 was obtained at 77 K in pseudomorphic In0.74Ga0.26As∕In0.46Al0.54As modulation-doped quantum well (MD-QW) grown on a (411)A InP substrate by molecular-beam epitaxy. This MD-QW has the “(411)A super-flat interfaces” (effectively atomically flat interfaces over a wafer-size area), which leads to significant reduction of interface roughness scattering at low temperatures. The highest electron mobility of the (411)A MD-QW was achieved by using pseudomorphic In0.46Al0.54As barriers. The electron mobility is 44% higher than that (73 000 cm2∕V s at 77 K) of a similar MD-QW structure grown on a conventional (100)InP substrate.
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81.07.St Quantum wells
81.05.Ea III-V semiconductors
73.63.Hs Quantum wells
68.65.Fg Quantum wells
73.50.Fq High-field and nonlinear effects
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Charge carrier transport in an emissive layer of green electrophosphorescent devices

Noriyuki Matsusue, Satoshi Ikame, Yuichiro Suzuki, and Hiroyoshi Naito

Appl. Phys. Lett. 85, 4046 (2004); http://dx.doi.org/10.1063/1.1813628 (3 pages) | Cited 36 times

Online Publication Date: 3 November 2004

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Charge carrier generation and transport in fac tris (2-phenylpyridine) iridium (III) (Ir(ppy)3) doped in 4,4′-N,N′-dicarbazole-biphenel (CBP) thin films have been studied in terms of time-of-flight and time-resolved photoluminescence spectroscopies. It is found that the excitation energy rapidly transfer from CBP to Ir(ppy)3, and that the charge carriers are generated on Ir(ppy)3 sites. With increasing Ir(ppy)3 concentration, the electron drift mobility is slightly decreased, while the hole transit signals become unobservable. The electron and hole transport properties of Ir(ppy)3 doped CBP thin films result from the energy levels of the lowest unoccupied molecular orbital and the highest occupied molecular orbital of Ir(ppy)3 with respect to those of CBP.
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85.60.Jb Light-emitting devices
78.66.Qn Polymers; organic compounds
73.50.Dn Low-field transport and mobility; piezoresistance
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.47.-p Spectroscopy of solid state dynamics
78.55.Kz Solid organic materials

Spectroscopic second harmonic generation measured on plasma-deposited hydrogenated amorphous silicon thin films

W. M. M. Kessels, J. J. H. Gielis, I. M. P. Aarts, C. M. Leewis, and M. C. M. van de Sanden

Appl. Phys. Lett. 85, 4049 (2004); http://dx.doi.org/10.1063/1.1812836 (3 pages) | Cited 9 times

Online Publication Date: 3 November 2004

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Optical second harmonic generation (SHG) has been measured for plasma-deposited thin films of hydrogenated amorphous silicon (a‐Si:H) at different polarization states for pump photon energies between 1.0 and 1.7 eV. Distinct resonance peaks are observed in this energy range and it is shown that the SH signal originates from an isotropic contribution at both the film-surface and substrate-interface region. The possibility that the SH signal originates from surface and interface dangling bond states of a‐Si:H is discussed.
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81.05.Cy Elemental semiconductors
68.55.-a Thin film structure and morphology
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
71.55.Cn Elemental semiconductors
73.20.At Surface states, band structure, electron density of states
78.66.Jg Amorphous semiconductors; glasses
78.66.Db Elemental semiconductors and insulators

Hydrogen plasma enhancement of boron activation in shallow junctions

A. Vengurlekar, S. Ashok, C. E. Kalnas, and N. D. Theodore

Appl. Phys. Lett. 85, 4052 (2004); http://dx.doi.org/10.1063/1.1811394 (3 pages) | Cited 2 times

Online Publication Date: 3 November 2004

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The ability to activate large concentrations of boron at lower temperatures is a persistent contingency in the continual drive for device scaling in Si microelectronics. We report on our experimental observations offering evidence for enhancement of electrical activation of implanted boron dopant in the presence of atomic hydrogen in silicon. This increased electrical activity of boron at lower anneal temperature is attributed to the creation of vacancies in the boron-implanted region, lattice-relaxation caused by the presence of atomic hydrogen, and the effect of atomic hydrogen on boron-interstitial cluster formation.
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61.72.uf Ge and Si
61.72.Cc Kinetics of defect formation and annealing
61.72.J- Point defects and defect clusters
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

A Raman scattering-based method to probe the carrier drift velocity in semiconductors: Application to gallium nitride

A. V. Andrade-Neto, A. R. Vasconcellos, R. Luzzi, and V. N. Freire

Appl. Phys. Lett. 85, 4055 (2004); http://dx.doi.org/10.1063/1.1808231 (3 pages) | Cited 4 times

Online Publication Date: 3 November 2004

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A single expression relating the carrier drift velocity in semiconductors under an electric field to Raman scattering data is derived resorting to a full nonequilibrium picture for electrons and holes. It allows one to probe with high optical precision both the ultrafast transient as well as the steady state carriers' drift velocity in semiconductor systems. This is achieved by simply modifying the experimental geometry, thus changing the angle between the transferred wave vector Q and the applied electric field E, and measuring the frequency shift promoted by the presence of the field to be observed in the single-particle and plasmon scattering spectra. An application to zinc-blende gallium nitride is presented to highlight the power of the method.
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78.30.Fs III-V and II-VI semiconductors
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
72.20.Fr Low-field transport and mobility; piezoresistance

Thermal stability of electron traps in GaN grown by metalorganic chemical vapor deposition

D. Johnstone, S. Doğan, J. Leach, Y. T. Moon, Y. Fu, Y. Hu, and H. Morkoç

Appl. Phys. Lett. 85, 4058 (2004); http://dx.doi.org/10.1063/1.1814801 (3 pages) | Cited 6 times

Online Publication Date: 3 November 2004

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Deep level transient spectroscopy was used to investigate the thermal stability of electron traps in n-type GaN grown by metalorganic chemical vapor deposition. The concentration of traps at 160 and at 500 K increased more than fivefold over the course of several 700 K anneal cycles, while a peak at 320 K increased by a factor of only 1.19. The increase in the trap concentration with repeated annealing might be due to a mobile trap or loss of passivant. Hydrogen is very likely present in high concentration in the epilayer, and its passivating effects may be lost with annealing.
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68.55.A- Nucleation and growth
73.61.Ey III-V semiconductors
65.40.-b Thermal properties of crystalline solids
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
81.40.Gh Other heat and thermomechanical treatments
81.65.Rv Passivation

Recombination activity of interstitial iron and other transition metal point defects in p- and n-type crystalline silicon

Daniel Macdonald and L. J. Geerligs

Appl. Phys. Lett. 85, 4061 (2004); http://dx.doi.org/10.1063/1.1812833 (3 pages) | Cited 56 times

Online Publication Date: 3 November 2004

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Interstitial iron in crystalline silicon has a much larger capture cross section for electrons than holes. According to the Shockley–Read–Hall model, the low-injection carrier lifetime in p-type silicon should therefore be much lower that in n-type silicon, while in high injection they should be equal. In this work we confirm this modeling using purposely iron-contaminated samples. A survey of other transition metal impurities in silicon reveals that those which tend to occupy interstitial sites at room temperature also have significantly larger capture cross sections for electrons. Since these are also the most probable metal point defects to occur during high temperature processing, using n-type wafers for devices such as solar cells may offer greater immunity to the effects of metal contaminants.
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81.05.Cy Elemental semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
61.72.J- Point defects and defect clusters
61.72.uf Ge and Si
61.72.S- Impurities in crystals

Critical point energy as a function of electric field determined by electroreflectance of surface-intrinsic-n+ type doped GaAs

Y. S. Chen, K. S. Wu, D. P. Wang, K. F. Huang, and T. C. Huang

Appl. Phys. Lett. 85, 4064 (2004); http://dx.doi.org/10.1063/1.1814794 (3 pages)

Online Publication Date: 3 November 2004

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Electroreflectance of surface-intrinsic-n+ type doped GaAs has been measured over a various biased voltage. The spectra have exhibited many Franz–Keldysh oscillations (FKOs) above band gap energy Eg. The electric field F and critical point energy Ec can be determined from the slope and intercept of FKOs fitting. Hence, we can obtain Ec as a function of F. In most of previous works, Ec is taken as Eg. However, it was found that Ec increases with F in this work. In order to explain this, the gain of energy of electron and hole in F was discussed.
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78.20.Jq Electro-optical effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Properties of highly Cr-doped AlN

A. Y. Polyakov, N. B. Smirnov, A. V. Govorkov, R. M. Frazier, J. Y. Liefer, G. T. Thaler, C. R. Abernathy, S. J. Pearton, and J. M. Zavada

Appl. Phys. Lett. 85, 4067 (2004); http://dx.doi.org/10.1063/1.1812845 (3 pages) | Cited 21 times

Online Publication Date: 3 November 2004

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Cr concentrations of ∼2 at. % were incorporated into AlN during growth by molecular beam epitaxy. Under optimized conditions, single-phase, insulating AlCrN is produced whose band gap shows a small (0.1–0.2 eV) decrease from the value for undoped AlN (6.2 eV), a decrease in a-plane lattice constant and the introduction of two absorption bands at 3 and 5 eV into the band gap. This material shows ferromagnetism with a Curie temperature above 300 K as judged from the difference in field-cooled and zero-field-cooled magnetization. For nonoptimized growth, second phases of Cr2N and AlxCry are produced in the AlN and the material is conducting (∼1000 Ω cm) with activation energy for conduction of 0.19 eV and apparent band gap of 5.8 eV.
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81.05.Ea III-V semiconductors
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
75.70.Ak Magnetic properties of monolayers and thin films
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
78.60.Hk Cathodoluminescence, ionoluminescence
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.S- Impurities in crystals
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

p-type ZnO films by monodoping of nitrogen and ZnO-based p–n homojunctions

J. M. Bian, X. M. Li, C. Y. Zhang, W. D. Yu, and X. D. Gao

Appl. Phys. Lett. 85, 4070 (2004); http://dx.doi.org/10.1063/1.1808229 (3 pages) | Cited 51 times

Online Publication Date: 3 November 2004

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Nitrogen-doped p-type ZnO (ZnO:N) films have been achieved by ultrasonic spray pyrolysis at atmosphere. The high structural quality of the obtained films was confirmed by x-ray diffraction, scanning electron microscopy, and photoluminescence spectra. Hall-effect and Seebeck-effect measurements indicate that the obtained p-type ZnO film shows a low resistivity of 3.02×10−2 Ω cm, high carrier concentration of 8.59×1018 cm−3, high mobility of 24.1 cm2∕V s, and high Seebeck coefficient of 408.2 μV∕K at room temperature. Furthermore, the two-layer structured ZnO p–n homojunctions were prepared by depositing n-type ZnO layer on p-type ZnO:N layer. The current–voltage curve derived from the two-layer structure clearly shows the typical rectifying characteristic of p–n junctions.
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81.05.Dz II-VI semiconductors
68.55.A- Nucleation and growth
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.uj III-V and II-VI semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
72.20.My Galvanomagnetic and other magnetotransport effects
72.20.Pa Thermoelectric and thermomagnetic effects
73.50.Lw Thermoelectric effects
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Ga II-VI semiconductors
78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
81.15.Rs Spray coating techniques
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
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Hysteretic current–voltage characteristics and resistance switching at a rectifying Ti∕Pr0.7Ca0.3MnO3 interface

A. Sawa, T. Fujii, M. Kawasaki, and Y. Tokura

Appl. Phys. Lett. 85, 4073 (2004); http://dx.doi.org/10.1063/1.1812580 (3 pages) | Cited 299 times

Online Publication Date: 3 November 2004

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We have characterized the vertical transport properties of epitaxial layered structures composed of Pr0.7Ca0.3MnO3(PCMO) sandwiched between SrRuO3(SRO) bottom electrode and several kinds of top electrodes such as SRO, Pt, Au, Ag, and Ti. Among the layered structures, Ti∕PCMO∕SRO is distinct due to a rectifying I–V characteristic with a large hysteresis. Corresponding to the hysteresis of the I–V characteristics, the contact resistance of the Ti∕PCMO interface reversibly switches between two stable states by applying pulsed voltage stress. We propose a model for the resistance switching at the Ti∕PCMO interface, in which the width and/or height of a Schottky-like barrier are altered by trapped charge carriers in the interface states.
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73.40.Ns Metal-nonmetal contacts
73.61.Le Other inorganic semiconductors
73.40.Cg Contact resistance, contact potential
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
81.05.Hd Other semiconductors

Observation of ferromagnetism above 900 K in Cr–GaN and Cr–AlN

H. X. Liu, Stephen Y. Wu, R. K. Singh, Lin Gu, David J. Smith, N. Newman, N. R. Dilley, L. Montes, and M. B. Simmonds

Appl. Phys. Lett. 85, 4076 (2004); http://dx.doi.org/10.1063/1.1812581 (3 pages) | Cited 97 times

Online Publication Date: 3 November 2004

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We report ferromagnetism at over 900 K in Cr–GaN and Cr–AlN thin films. The magnetic properties vary as a function of Cr concentration with 60%, and 20%, of the Cr being magnetically active at 3% doping in GaN, and 7% in AlN, respectively. In the GaN sample with the highest magnetically active Cr (60%), channeling Rutherford backscattering indicates that over 70% of Cr impurities are located on substitutional sites. These results give indisputable evidence that substitutional Cr defects are involved in the magnetic behavior. While Cr–AlN is highly resistive, Cr–GaN exhibits properties characteristic of hopping conduction including T−1∕2 resistivity dependence and small Hall mobility (0.06 cm2∕V s). A large negative magnetoresistance is attributed to the influence of the magnetic field on the quantum interference between the many paths linking two hopping sites. The results strongly suggest that ferromagnetism in Cr–GaN and Cr–AlN can be attributed to the double exchange mechanism as a result of hopping between near-midgap substitutional Cr impurity bands.
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75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
68.55.-a Thin film structure and morphology
75.70.Ak Magnetic properties of monolayers and thin films
73.61.Ey III-V semiconductors
75.30.Cr Saturation moments and magnetic susceptibilities
61.72.S- Impurities in crystals
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
73.50.Dn Low-field transport and mobility; piezoresistance
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.47.Pq Other materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Control of the magnetic anisotropy of epitaxially grown MnAs∕GaAs ferromagnet-semiconductor hybrid superlattices

J. H. Song, J. J. Lee, Y. Cui, J. B. Ketterson, and Sunglae Cho

Appl. Phys. Lett. 85, 4079 (2004); http://dx.doi.org/10.1063/1.1813630 (3 pages) | Cited 4 times

Online Publication Date: 3 November 2004

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Epitaxial hybrid structures of the ferromagnet–semiconductor superlattice MnAs∕GaAs were grown on GaAs(001) substrates by molecular-beam epitaxy and the dependence of the magnetic properties on the growth temperature and the periodicity were characterized. The magnetic anisotropy is strongly dependent on the surface reconstruction of GaAs(001) substrates. The increase of the periodicity from 5 nm∕5 nm to 10 nm∕10 nm also changes the magnetic anisotropy. These results demonstrate that the surface reconstruction of the substrate and the periodicity determine the magnetic structure of the MnAs∕GaAs superlattices.
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68.65.Cd Superlattices
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
81.05.Ea III-V semiconductors
68.55.A- Nucleation and growth
75.30.Gw Magnetic anisotropy
68.35.B- Structure of clean surfaces (and surface reconstruction)
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Atomic-scale structural analyses of epitaxial Co∕Re superlattices

Wentao Xu, Lance E. De Long, Timothy Charlton, Matthew Chisholm, and David Lederman

Appl. Phys. Lett. 85, 4082 (2004); http://dx.doi.org/10.1063/1.1813626 (3 pages) | Cited 1 time

Online Publication Date: 3 November 2004

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High-resolution transmission electron microscopy and scanning transmission electron microscopy (STEM) have been used to investigate atomic-scale structural properties of Co∕Re trilayers and superlattices grown via magnetron sputtering. The sample growth was epitaxial with the (10math0) plane of Co and Re parallel to the (11math0) plane of Al2O3, and the [001] direction of Re and Co coinciding with that of the Al2O3. Both low-angle and high-angle Z-contrast STEM images show a very uniform layer thickness. However, the interface roughness between the Re and Co layers monotonically increases with interface distance from the substrate. These results strongly imply that, in the epitaxial Re∕Co superlattice system, interface roughness plays a more important role in the giant magnetoresistance effect than thickness fluctuations of the spacer layer. Previous anisotropic magnetoresistance measurements can be explained in terms of the observed atomic-scale structure.
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68.65.Cd Superlattices
68.65.Ac Multilayers
75.47.De Giant magnetoresistance
72.15.Gd Galvanomagnetic and other magnetotransport effects
68.35.Ct Interface structure and roughness
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Gw Magnetic anisotropy
81.15.Cd Deposition by sputtering
68.37.Lp Transmission electron microscopy (TEM)

Domain-size-dependent exchange bias in Co∕LaFeO3

A. Scholl, F. Nolting, J. W. Seo, H. Ohldag, J. Stöhr, S. Raoux, J.-P. Locquet, and J. Fompeyrine

Appl. Phys. Lett. 85, 4085 (2004); http://dx.doi.org/10.1063/1.1813633 (3 pages) | Cited 16 times

Online Publication Date: 3 November 2004

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X-ray microscopy using magnetic linear dichroism of a zero-field-grown multidomain Co∕LaFeO3 ferromagnet∕antiferromagnet sample shows a local exchange bias of random direction and magnitude. A statistical analysis of the local bias of individual micron-size magnetic domains demonstrates an increasing bias field with decreasing domain size as expected for a random distribution of pinned, uncompensated spins, which are believed to mediate the interface coupling. A linear dependence with the inverse domain diameter is found.
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75.50.Cc Other ferromagnetic metals and alloys
75.50.Ee Antiferromagnetics
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Ch Domain walls and domain structure
68.37.Yz X-ray microscopy
75.30.Et Exchange and superexchange interactions

Flux pinning behavior of incomplete multilayered lattice structures in YBa2Cu3O7−d

Paul N. Barnes, Timothy J. Haugan, Chakrapani V. Varanasi, and Timothy A. Campbell

Appl. Phys. Lett. 85, 4088 (2004); http://dx.doi.org/10.1063/1.1809274 (3 pages) | Cited 31 times

Online Publication Date: 3 November 2004

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Magnetization results of YBa2Cu3O7−d films processed with interlayers of CeO2 inclusions are presented. Unexpected flux pinning results that are different from previous observations with nanoparticulate layered inclusions were observed. Flux pinning was found to be in some cases either slightly improved at either low fields <0.5 T or in other cases at high fields >8 T although degraded, sometimes severely, at interim magnetic fields. Most unexpectedly, the pinning performance of the various samples rapidly converges as the temperature is reduced from 77 to 65 K, causing all films to have similar Jc(H) behavior at 65 K even though dramatically different at 77 K.
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74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.25.Ha Magnetic properties including vortex structures and related phenomena
61.72.Qq Microscopic defects (voids, inclusions, etc.)
74.25.Sv Critical currents

Bistable superconducting quantum interference device with built-in switchable π∕2 phase shift

Henk-Jan H. Smilde, Ariando, Horst Rogalla, and Hans Hilgenkamp

Appl. Phys. Lett. 85, 4091 (2004); http://dx.doi.org/10.1063/1.1812813 (3 pages) | Cited 8 times

Online Publication Date: 3 November 2004

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Superconducting quantum interference devices (SQUIDs) have been realized with a built-in π∕2 phase shift of the superconducting wave function. Its design is inspired by the phase-shifter concept, first proposed by Ioffe et al. [Nature 398, 679 (1999)] as the key element in a solid-state qubit configuration. It exploits the dx2−y2 order parameter symmetry in the high-Tc cuprates in multilayer structures based on YBa2Cu3O7-Nb ramp-type Josephson contacts. By reversing the sign of the persistent circulating current in the phase-shifting element, the π∕2 SQUID can be controllably switched between two energetically degenerate ground states, with complementary magnetic flux dependencies.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
73.23.Ra Persistent currents
74.25.Sv Critical currents

Precession-dominated switching of synthetic antiferromagnets

Joo-Von Kim, T. Devolder, C. Chappert, C. Maufront, and R. Fournel

Appl. Phys. Lett. 85, 4094 (2004); http://dx.doi.org/10.1063/1.1812576 (3 pages) | Cited 5 times

Online Publication Date: 3 November 2004

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We present theoretical results of precession-dominated switching of synthetic antiferromagnet elements. A fast (subnanosecond) reversal mode is shown to be possible for perfectly compensated structures (zero net moment) with pulsed magnetic fields, where the antiparallel alignment is largely preserved during reversal. By using component ferromagnets with different magnetocrystalline and shape anisotropies, we show that it is possible to select the final magnetic state of the synthetic antiferromagnet with pulsed fields alone. Applications to magnetic memory devices are discussed.
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75.50.Bb Fe and its alloys
75.50.Ee Antiferromagnetics
75.30.Cr Saturation moments and magnetic susceptibilities
75.30.Gw Magnetic anisotropy

Enhancement of rare-earth–transition-metal exchange interaction in Pr2Fe17 probed by inelastic neutron scattering

N. Magnani, S. Carretta, G. Amoretti, L. Pareti, A. Paoluzi, R. Caciuffo, and J. A. Stride

Appl. Phys. Lett. 85, 4097 (2004); http://dx.doi.org/10.1063/1.1814819 (3 pages) | Cited 2 times

Online Publication Date: 3 November 2004

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The fundamental magnetic interactions of Pr2Fe17 are studied by inelastic neutron scattering and anisotropy field measurements. Data analysis confirms the presence of three magnetically inequivalent sites, and reveals an exceptionally large value of the exchange field. The unexpected importance of J-mixing effects in the description of the ground-state properties of Pr2Fe17 is shown, and possible applications of related compounds are envisaged.
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75.50.Bb Fe and its alloys
75.30.Et Exchange and superexchange interactions
75.30.Gw Magnetic anisotropy

Magnetic anisotropy of Fe3Pt alloy thin films

M. A. I. Nahid and Takao Suzuki

Appl. Phys. Lett. 85, 4100 (2004); http://dx.doi.org/10.1063/1.1815070 (3 pages) | Cited 6 times

Online Publication Date: 3 November 2004

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The magnetic anisotropy constants of Fe3Pt alloy thin films grown onto MgO(100) and MgO(111) substrates by electron-beam evaporation are investigated in conjunction with structure. It is observed that the orientation of the Fe3Pt films depends on the substrate. Both oriented samples exhibit very large in-plane magnetic anisotropy. The magnetic anisotropy constants K1 and K2 are found to strongly depend on the deposition temperature (TS). The maximum values of K1 and K2 obtained are about −4×106 and 2×107 erg∕cc, respectively. A close relationship is observed between the magnetic anisotropy constants and structural parameter.
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75.50.Bb Fe and its alloys
75.30.Gw Magnetic anisotropy
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
75.70.Ak Magnetic properties of monolayers and thin films
68.55.-a Thin film structure and morphology
68.55.A- Nucleation and growth

Magnetic and morphological characteristics of nickel nanoparticles films produced by femtosecond laser ablation

G. Ausanio, A. C. Barone, V. Iannotti, L. Lanotte, S. Amoruso, R. Bruzzese, and M. Vitiello

Appl. Phys. Lett. 85, 4103 (2004); http://dx.doi.org/10.1063/1.1815065 (3 pages) | Cited 24 times

Online Publication Date: 3 November 2004

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We have used the technique of femtosecond (fs) laser ablation in a vacuum to produce films of nickel nanoparticles. A peculiarity of this fs laser deposition is the significant shape and orientation anisotropy of the nanoparticles, which are oblate ellipsoids with the major axis parallel to the deposition substrate. The deposited films present unique magnetic properties, and, in specific conditions, very high remanence ratios (up to 0.7) accompanied with relatively low values of saturation and coercive fields can be obtained. We have interpreted these results in terms of the mentioned anisotropies, and of the occurrence of a thermally induced in-plane tensile stress, which is a function of the nanoparticles size.
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81.07.Wx Nanopowders
75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Cc Other ferromagnetic metals and alloys
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.46.-w Structure of nanoscale materials
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.Fg Pulsed laser ablation deposition
78.47.-p Spectroscopy of solid state dynamics
68.60.Bs Mechanical and acoustical properties
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Abnormal temperature dependence of dielectric constant in (Ba0.7Sr0.3)TiO3 thin films

Hao Yang, Jun Miao, Bin Chen, Li Zhao, Bo Xu, Xiaoli Dong, Lixin Cao, Xianggang Qiu, and Bairu Zhao

Appl. Phys. Lett. 85, 4106 (2004); http://dx.doi.org/10.1063/1.1812575 (3 pages) | Cited 2 times

Online Publication Date: 3 November 2004

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Pt∕(Ba0.7Sr0.3)TiO3∕YBa2Cu3O7−x capacitors were fabricated on LaAlO3 substrates. Dielectric and ferroelectric properties were measured in the temperature range from 20 to 250 K. It was found that the dielectric constant decreased with decreasing temperature from 250 to ∼150 K but then increased as the temperature continued to decrease to 20 K. Considering this phenomenon along with the irregular temperature dependence of spontaneous polarization, it is indicated that such abnormal behavior originates in a second-order structural phase transition in the (Ba1−xSrx)TiO3 thin film in the vicinity of 150 K.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.80.B- Phase transitions and Curie point
77.22.Ch Permittivity (dielectric function)
77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization
84.32.Tt Capacitors
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
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