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29 Mar 1999

Volume 74, Issue 13, pp. 1785-1922

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Controlled underdoping of cuprates using ultraviolet radiation

P. Schwaller, S. Berner, T. Greber, J. Osterwalder, and H. Berger

Appl. Phys. Lett. 74, 1877 (1999); http://dx.doi.org/10.1063/1.123699 (3 pages)

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A method for a controlled change of the doping level of high-temperature superconductors with ultraviolet radiation is presented. With photoemission it is shown that the exposure of Bi2Sr2CaCu2O8+δ samples to the light of a He gas-discharge lamp causes oxygen desorption. From measurements of the Fermi surface, it is found that the oxygen desorption causes a decrease of the doping level of the superconductors. From the desorption cross sections that strongly depend on the photon energy, two different oxygen desorption channels are inferred. This procedure for decreasing the doping level has the advantage that the crystallinity of the sample is not altered and that the doping level can be simultaneously measured by photoelectron spectroscopy. © 1999 American Institute of Physics.
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74.72.-h Cuprate superconductors
74.25.Jb Electronic structure (photoemission, etc.)
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
79.60.-i Photoemission and photoelectron spectra
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Nonlinear magneto-optical diffraction from periodic domain structures in magnetic films

N. N. Dadoenkova, I. L. Lyubchanskii, M. I. Lyubchanskii, and Th. Rasing

Appl. Phys. Lett. 74, 1880 (1999); http://dx.doi.org/10.1063/1.123700 (3 pages) | Cited 11 times

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The nonlinear optical diffraction in magnetic films with a laminar domain structure and Bloch-type domain walls is investigated for both s and p polarization of incident light. It is shown that the contribution of magnetic domains and domain walls to the nonlinear diffraction can be separated by a polarization analysis of the scattered light. © 1999 American Institute of Physics.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.60.Ch Domain walls and domain structure
78.20.Ls Magneto-optical effects
42.65.-k Nonlinear optics
42.25.Fx Diffraction and scattering
42.25.Ja Polarization

Width dependence of giant magnetoresistance in Cu/Co multilayer nanowires

J. A. Katine, A. Palanisami, and R. A. Buhrman

Appl. Phys. Lett. 74, 1883 (1999); http://dx.doi.org/10.1063/1.123701 (3 pages) | Cited 11 times

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Electron beam lithography and ion milling have been used to pattern sputtered Cu/Co multilayer wires ranging in width from 750 to 35 nm. Samples having Cu thicknesses which correspond to the first, second, and third antiferromagnetic coupling maxima have been measured. Contrary to expectation, enhancement in the amplitude of the giant magnetoresistance with decreasing width was not observed. © 1999 American Institute of Physics.
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75.47.De Giant magnetoresistance
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.15.Cd Deposition by sputtering
81.20.Wk Machining, milling

Ferromagnetism at room temperature in La0.8Ca0.2MnO3 thin films

R. Shreekala, M. Rajeswari, R. C. Srivastava, K. Ghosh, A. Goyal, V. V. Srinivasu, S. E. Lofland, S. M. Bhagat, M. Downes, R. P. Sharma, S. B. Ogale, R. L. Greene, R. Ramesh, T. Venkatesan, R. A. Rao, et al.

Appl. Phys. Lett. 74, 1886 (1999); http://dx.doi.org/10.1063/1.123702 (3 pages) | Cited 28 times

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Anomalously high metal–insulator transition temperature Tp and ferromagnetic transition temperature Tc have been observed in thin films of La0.8Ca0.2MnO3. Ferromagnetic resonance signals from microwave studies are observed at room temperature (well above Tc) suggesting the presence of multiple magnetic spin systems. The Tp and Tc values are higher than that of La0.67Ca0.33MnO3 which have the highest Tp and Tc according to the bulk phase diagram. These results suggest that properties well beyond those seen in the bulk phase diagram may be achievable in thin films of the manganites. © 1999 American Institute of Physics.
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75.50.Dd Nonmetallic ferromagnetic materials
75.70.Ak Magnetic properties of monolayers and thin films
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.47.De Giant magnetoresistance
71.30.+h Metal-insulator transitions and other electronic transitions
72.60.+g Mixed conductivity and conductivity transitions
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Magnetic and hardness properties of nanostructured Ni–Co films deposited by a nonaqueous electroless method

G. M. Chow, J. Ding, J. Zhang, K. Y. Lee, D. Surani, and S. H. Lawrence

Appl. Phys. Lett. 74, 1889 (1999); http://dx.doi.org/10.1063/1.123703 (3 pages) | Cited 19 times

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Nanostructured NixCo100−x films were deposited on Cu substrates by reducing the constituent metal salts in refluxing ethylene glycol at 194 °C. The average crystallite size increased with x, and reached a maximum of 64 nm when x = 100. The coercivity Hc of the films measured in the direction perpendicular (⊥) to the plane of the film was higher than that in the parallel (∥) direction. For the sample of x = 50, Hc⊥ was 379 Oe, which was six times that of Hc∥. Saturation magnetization Ms in the film plane was 1016 emu/cm3, and the remanent magnetization Mr 636 emu/cm3, giving a squareness ratio of 0.63. This film also had a Vickers hardness of 193. © 1999 American Institute of Physics.
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75.50.Kj Amorphous and quasicrystalline magnetic materials
68.60.Bs Mechanical and acoustical properties
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.07.-b Nanoscale materials and structures: fabrication and characterization
62.20.Qp Friction, tribology, and hardness
81.15.Pq Electrodeposition, electroplating
75.50.Cc Other ferromagnetic metals and alloys
75.30.Gw Magnetic anisotropy

2 THz bandwidth electrical pulses on Au and YBa2Cu3Ox transmission lines

Christian J. Osbahr, Britt H. Larsen, Thorsten Holst, Yueqiang Shen, and Søren R. Keiding

Appl. Phys. Lett. 74, 1892 (1999); http://dx.doi.org/10.1063/1.123704 (3 pages) | Cited 5 times

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An amorphous photoconductive GaAs switch is laser ablated directly onto a superconducting YBa2Cu3Ox coplanar transmission line structure. Illuminating the switch with femtosecond laser pulses generates electrical pulses containing frequency components up to 2 THz. The pulses are detected by photoconductive sampling and have a full width at half maximum of 0.4 ps without deconvolution. Measurements have been performed on both YBa2Cu3Ox and Au/YBa2Cu3Ox transmission lines and we find attenuation and dispersion coefficients to be larger on YBa2Cu3Ox at 77 K than on Au. Furthermore, the integrated photoconductive switch is used to demonstrate that subpicosecond pulses can propagate through small gaps in the transmission lines with minimum attenuation and dispersion. © 1999 American Institute of Physics.
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84.40.Az Waveguides, transmission lines, striplines
85.25.Hv Superconducting logic elements and memory devices; microelectronic circuits
85.60.-q Optoelectronic devices
74.72.-h Cuprate superconductors
81.15.Fg Pulsed laser ablation deposition
85.40.Sz Deposition technology

Hot-electron energy relaxation, noise, and lattice strain in InGaAs quantum well channels

A. Matulionis, V. Aninkevičius, J. Liberis, I. Matulionienė, J. Berntgen, K. Heime, and H. L. Hartnagel

Appl. Phys. Lett. 74, 1895 (1999); http://dx.doi.org/10.1063/1.123705 (3 pages) | Cited 5 times

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Energy loss by hot electrons in lattice-matched and strained InGaAs layers is estimated from experimental data on microwave noise obtained for InP-based quantum well channels containing two-dimensional electron gas. A strong correlation of the energy relaxation time and the lattice strain is observed. © 1999 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Td Noise processes and phenomena
73.50.Fq High-field and nonlinear effects
73.61.Ey III-V semiconductors

Magnetoresistance of single-domain ferromagnetic particles

J. Aumentado and V. Chandrasekhar

Appl. Phys. Lett. 74, 1898 (1999); http://dx.doi.org/10.1063/1.123706 (3 pages) | Cited 17 times

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We have performed magnetoresistance measurements on single-domain, submicron elliptical Ni particles using nonmagnetic probes in a four-probe geometry at liquid-helium temperatures. In the smallest particles, the magnetoresistance shows sharp jumps which are associated with the switching of individual domains. Using an anisotropic magnetoresistance model, we can reconstruct hysteresis loops of the normalized magnetization. The remanent magnetization in zero applied magnetic field is typically 15% less than the saturation magnetization. This relaxation of the magnetization may be due to surface effects or crystal grain structure in the particles. © 1999 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
72.15.Gd Galvanomagnetic and other magnetotransport effects
75.60.Ch Domain walls and domain structure
75.50.Cc Other ferromagnetic metals and alloys
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