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23 Jul 2001

Volume 79, Issue 4, pp. 449-553

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Atomic scale investigations of the Co/Pt(111) interface structure and magnetic properties

D. W. Moon, Y. H. Ha, Y. Park, J.-W. Lee, J. Kim, and S.-C. Shin

Appl. Phys. Lett. 79, 503 (2001); http://dx.doi.org/10.1063/1.1388156 (3 pages) | Cited 5 times

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The interface structure of an ultrathin Co overlayer on a Pt(111) crystal was investigated with atomic-layer resolution medium-energy ion scattering spectroscopy and surface magneto-optical Kerr effect (SMOKE). For a 7 ML Co, interdiffusion begins at 673 K to form a heavily distorted Co–Pt surface alloy layer with little change in SMOKE intensity. However, annealing at 773 K formed a 30 atomic-layer-thick Co–Pt substitutional alloy with 3.7% maximum tensile strain, at which the SMOKE intensity increased more than 200%. The enhancement of the Kerr intensity is discussed with the interface alloy formation. © 2001 American Institute of Physics.
Show PACS
68.35.Fx Diffusion; interface formation
68.35.Ct Interface structure and roughness
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
78.20.Ls Magneto-optical effects
75.30.Gw Magnetic anisotropy
78.66.Bz Metals and metallic alloys
75.70.Ak Magnetic properties of monolayers and thin films
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Colossal magnetoresistance in doped manganites: A consequence of percolation and phase separation

A. K. Pradhan, Y. Feng, B. K. Roul, and D. R. Sahu

Appl. Phys. Lett. 79, 506 (2001); http://dx.doi.org/10.1063/1.1388158 (3 pages) | Cited 15 times

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We report measurements of the resistivity and magnetization of high-quality melt-processed La0.67Ca0.33MnO3 (LCM) and Sr-doped LCM materials that exhibit a sharp and enhanced metal–insulator transition (TMI) with significant colossal magnetoresistance (CMR) and two competing magnetic phases in the vicinity of TMI. Our results can well be explained using percolation in combination with the phase-separation scenario proposed for CMR. We propose that the spin polarization through grain boundaries and the enhanced grain connectivity between the ferromagnetic domains facilitate better percolation through a junction and filament-like resistor network. © 2001 American Institute of Physics.
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75.47.Gk Colossal magnetoresistance
71.30.+h Metal-insulator transitions and other electronic transitions
61.72.Mm Grain and twin boundaries
75.50.Dd Nonmetallic ferromagnetic materials

Scaling behavior of higher harmonic responses in textured (Bi,Pb)2Sr2Ca2Cu3Oy/Ag tapes

Y. J. Zhang and C. K. Ong

Appl. Phys. Lett. 79, 509 (2001); http://dx.doi.org/10.1063/1.1388155 (3 pages)

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A silver-sheathed (Bi,Pb)2Sr2Ca2Cu3Oy tape was studied in terms of harmonic responses χn = χn′−iχn″ (n = 3, 5, 7) to reveal the angular dependence of its physical properties. In the screening method higher harmonic responses are directly related to the nonlinear voltage–current [E(J)] relation of the sample. Therefore, the effect of the silver sheath on the harmonic measurements can be neglected. We performed measurements of the harmonic responses as a function of applied magnetic field or angle between the magnetic field and the tape plane at various temperatures. The measured data could be scaled onto a single curve by using the three-dimensional scaling relation. The derived anisotropic parameter γ ranged from 5.1 to 5.6 at the measured temperature region. Such a small γ value was attributed to the misalignment of the grains in the tape. © 2001 American Institute of Physics.
Show PACS
74.72.-h Cuprate superconductors
84.71.Mn Superconducting wires, fibers, and tapes
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition

Correlation of power handling capability and intermodulation distortion in YBa2Cu3O7−δ thin films

P. Lahl, R. Wördenweber, and M. Hein

Appl. Phys. Lett. 79, 512 (2001); http://dx.doi.org/10.1063/1.1383272 (3 pages) | Cited 13 times

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The nonlinearity of the microwave properties of coplanar thin-film YBa2Cu3O7−δ resonators are examined by measurements of the degradation of the quality factor QL and the increase of the two-tone third-order intermodulation distortion signal with increasing microwave power. A linear correlation between the data of the characteristic microwave powers, which are obtained for the degradation of QL and the intermodulation signal, is experimentally observed and explained in terms of a theoretical model based solely on well-known expressions for the nonlinear surface resistance. Due to these experimental observations and the theoretical model, we conclude, that the degradation of the resonator Q factor and the generation of intermodulation distortion are determined by the same physical mechanism and that thermal effects can most likely be excluded. © 2001 American Institute of Physics.
Show PACS
74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
85.25.-j Superconducting devices
84.40.Az Waveguides, transmission lines, striplines
72.30.+q High-frequency effects; plasma effects
73.25.+i Surface conductivity and carrier phenomena
74.25.N- Response to electromagnetic fields
74.25.F- Transport properties
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