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27 Dec 1999

Volume 75, Issue 26, pp. 4049-4210

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The generation and detection of high flux atomic oxygen for physical vapor deposition thin film growth

N. J. C. Ingle, R. H. Hammond, M. R. Beasley, and D. H. A. Blank

Appl. Phys. Lett. 75, 4162 (1999); http://dx.doi.org/10.1063/1.125569 (3 pages) | Cited 15 times

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The growth of many epitaxial thin-film oxides is significantly enhanced with the use of an oxidizing agent such as atomic oxygen, ozone, or NO2. We developed a flow-through microwave plasma source to generate large atomic oxygen fluxes while maintaining vacuum pressures of less that 1×10−4 Torr. Continuous and real-time detection of the atomic oxygen was achieved by atomic absorption of the 130 nm atomic oxygen lines. Atomic oxygen fluxes of at least 1.4×1018 atoms/cm2 s and dissociation efficiencies of around 100% were obtained. © 1999 American Institute of Physics.
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52.50.Dg Plasma sources
81.15.Kk Vapor phase epitaxy; growth from vapor phase
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods

Effective microwave surface resistance of gold-contacted YBa2Cu3O7−x thin films

A. G. Zaitsev, R. Schneider, J. Geerk, G. Linker, F. Ratzel, and R. Smithey

Appl. Phys. Lett. 75, 4165 (1999); http://dx.doi.org/10.1063/1.125570 (3 pages) | Cited 9 times

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The microwave surface resistance (Rs) of YBa2Cu3O7−x (YBCO) films sputtered simultaneously on both sides of CeO2 coated sapphire wafers of 3 in. diameter was measured using the disk resonator technique at a frequency of 1.92 GHz. By deposition of Au layers of various thicknesses on the unpatterned YBCO side of the disk resonator, we studied the effective Rs of the Au-contacted YBCO films. Although the Au layer was not directly exposed to the microwave power, it dramatically increased the effective Rs of the YBCO film. For example, Rs(77 K) = 16.5 μΩ of a 300-nm-thick YBCO film increased to 85 μΩ by the deposition of a 0.1-μm-thick Au layer. The increase of the Au thickness to 1.2 μm resulted in a further enhancement of the effective Rs up to 560 μΩ. We explain this effect in terms of the impedance transformation model. According to this model the effective Rs of the Au/YBCO bilayer decreases with increasing YBCO film thickness. However, Au layers with thicknesses above 1 μm considerably enhance the effective Rs even for thick YBCO films (700–800 nm). A higher quality of the YBCO films (in terms of shorter London penetration depths) reduces the effect of a Au layer, while a low electrical resistivity of this layer leads to a further increase of the effective Rs. © 1999 American Institute of Physics.
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74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
74.25.F- Transport properties
74.25.N- Response to electromagnetic fields
73.25.+i Surface conductivity and carrier phenomena
72.30.+q High-frequency effects; plasma effects
74.25.Ha Magnetic properties including vortex structures and related phenomena

Self-assembly of floating magnetic particles into ordered structures: A promising route for the fabrication of tunable photonic band gap materials

M. Golosovsky, Y. Saado, and D. Davidov

Appl. Phys. Lett. 75, 4168 (1999); http://dx.doi.org/10.1063/1.125571 (3 pages) | Cited 50 times

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We report stable ordered arrays of millimeter-size magnetic particles floating on a liquid surface. Self-assembly into a regular two-dimensional lattice results from lateral magnetic interactions between the particles. The lattice constant may be easily tuned by the application of external magnetic field. The array symmetry is designed by using different particle shapes, magnets, and magnet position inside the particle, so that complex symmetries may be achieved. Three-dimensional ordered arrays are obtained in a stack of troughs containing floating magnets. Computer simulations of electromagnetic wave propagation in such three-dimensional structures suggest an opening of a tunable photonic band gap in the microwave range. © 1999 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
68.18.-g Langmuir-Blodgett films on liquids
42.50.-p Quantum optics
42.70.Qs Photonic bandgap materials
41.20.Jb Electromagnetic wave propagation; radiowave propagation
81.05.Zx New materials: theory, design, and fabrication

Microstructure-dependent coercivity in monodispersed hematite particles

C. Rath, K. K. Sahu, S. D. Kulkarni, S. Anand, S. K. Date, R. P. Das, and N. C. Mishra

Appl. Phys. Lett. 75, 4171 (1999); http://dx.doi.org/10.1063/1.125572 (3 pages) | Cited 25 times

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Microstructure and magnetic properties of monodispersed pseudocubic and trapezoidal particles with varying sizes prepared through the hydrothermal precipitation route are reported. The coercivity for trapezoidal particles was similar to that of reported values. For pseudocubic particles, however, the coercivity is unusually high (∼6 kOe) as compared to the maximum value (3 kOe) reported in the literature. Detailed microstructural analysis revealed that particles with a well-defined shape are, in fact, polycrystalline. The high coercivity and its variation with particle shape and size are correlated to the internal nanostructure of the particles. © 1999 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
61.46.-w Structure of nanoscale materials
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
64.75.-g Phase equilibria
81.30.Mh Solid-phase precipitation
81.40.Rs Electrical and magnetic properties related to treatment conditions

Magnetic configurations in exchange-biased double superlattices

S. G. E. te Velthuis, G. P. Felcher, J. S. Jiang, A. Inomata, C. S. Nelson, A. Berger, and S. D. Bader

Appl. Phys. Lett. 75, 4174 (1999); http://dx.doi.org/10.1063/1.125573 (3 pages) | Cited 21 times

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The layer-by-layer magnetization of a “double-superlattice” Fe/Cr(211) exchange-bias junction was determined by polarized neutron reflectometry. An n-layered [Fe/Cr]n antiferromagnetic (AF) superlattice is coupled with an m-layered [Fe/Cr]m ferromagnetic (F) superlattice, to provide a controlled exchange bias. In low magnetic fields, the magnetizations of the two superlattices are collinear. The two magnetized states (along or opposite to the bias field) differ only in the relative orientation of the F and adjacent AF layer. At higher fields, the AF moments flop to the direction perpendicular to the applied field. The structure, thus determined, explains the magnitude of the bias field. © 1999 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.30.Et Exchange and superexchange interactions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy
75.50.Bb Fe and its alloys
75.50.Ee Antiferromagnetics

Suppression of growth-induced perpendicular magnetic anisotropy in Co–Pt alloys by trace amounts of Si

A. L. Shapiro, O. Vajk, F. Hellman, K. M. Ring, and K. L. Kavanagh

Appl. Phys. Lett. 75, 4177 (1999); http://dx.doi.org/10.1063/1.125574 (3 pages)

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(CoxPt1−x)1−ySiy alloys with Si content from 1 to 20 at. % have been grown over a range of growth conditions. Co-deposition of even trace amounts of Si with Co–Pt alloys causes the growth-induced magnetic anisotropy and chemical clustering found in these vapor-deposited alloy films to decrease or vanish. It also causes significant reduction in grain size. Addition of 5 at. % Si eliminates anisotropy completely. Addition of 1 at. % Si produces a film with magnetic properties identical to pure Co–Pt alloys grown at lower deposition temperatures. We suggest this suppression of anisotropy and related effects are due to a decrease in surface mobility during growth in the presence of even trace amounts of Si. © 1999 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.30.Gw Magnetic anisotropy
81.40.Rs Electrical and magnetic properties related to treatment conditions
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
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