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29 Jul 2002

Volume 81, Issue 5, pp. 789-944

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Degradation of LaMnO3−y surface layer in LaMnO3−y/metal interface

A. Plecenik, K. Fröhlich, J. P. Espinós, J. P. Holgado, A. Halabica, M. Pripko, and A. Gilabert

Appl. Phys. Lett. 81, 859 (2002); http://dx.doi.org/10.1063/1.1497439 (3 pages) | Cited 16 times

Online Publication Date: 22 July 2002

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We report electrical measurements showing the degradation processes of LaMnO3−y (LaMnO) in LaMnO/normal metal interface in both point contact and planar-type junctions. The time evolution of the junction resistance is characterized by the appearance of a second maximum in the resistance versus temperature dependence (R–T) that occurs at a temperature lower than that for the metal–insulator transition in the bulk. These effects are explained in terms of the formation of a depleted interface layer in LaMnO caused by an out-diffusion of oxygen from the manganite surface to the normal metal. This was confirmed by XPS measurements. Similar results on LaSrMnO3−y/metal interfaces were also obtained. © 2002 American Institute of Physics.
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68.35.Fx Diffusion; interface formation
71.30.+h Metal-insulator transitions and other electronic transitions
73.40.Ns Metal-nonmetal contacts
79.60.Jv Interfaces; heterostructures; nanostructures

Current-controlled bi-stable domain configurations in Ni81Fe19 elements: An approach to magnetic memory devices

H. Koo, C. Krafft, and R. D. Gomez

Appl. Phys. Lett. 81, 862 (2002); http://dx.doi.org/10.1063/1.1495883 (3 pages) | Cited 31 times

Online Publication Date: 22 July 2002

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The discovery of current-switchable bi-stable remanent domain configurations on small ferromagnetic islands is reported. Rectangular NiFe islands with a thickness of 50 to 100 nm and lateral dimensions on the order of several microns were imaged using magnetic force microscopy after application of 10 ns current pulses through the material. The closure configuration can be set into either the 4 or 7 domain configuration by applying positive or negative current polarity at density on the order 107 A/cm2. The chirality of the closure patterns is fixed, implying that only two rather than four states are stable in these patterns. The possibility of using these configurations as a means of storing a logic state for memory applications is discussed. © 2002 American Institute of Physics.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.60.Ch Domain walls and domain structure
75.50.Bb Fe and its alloys

High resolution magnetic force microscopy using focused ion beam modified tips

G. N. Phillips, M. Siekman, L. Abelmann, and J. C. Lodder

Appl. Phys. Lett. 81, 865 (2002); http://dx.doi.org/10.1063/1.1497434 (3 pages) | Cited 36 times

Online Publication Date: 22 July 2002

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Atomic force microscope tips coated by the thermal evaporation of a magnetic 30 nm thick Co film have been modified by focused ion beam milling with Ga+ ions to produce tips suitable for magnetic force microscopy. Such tips possess a planar magnetic element with high magnetic shape anisotropy, an extremely high aspect ratio of greater than 30:1, and an end radius of less than 25 nm. These tips have been used in a commercial atomic force microscope under ambient conditions to obtain 30 nm resolution magnetic images of an established CoNi/Pt multilayer reference sample. © 2002 American Institute of Physics.
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07.79.Pk Magnetic force microscopes
07.79.Lh Atomic force microscopes
75.70.Ak Magnetic properties of monolayers and thin films
75.30.Gw Magnetic anisotropy

Very high trapped fields in neutron irradiated and reinforced YBa2Cu3O7−δ melt-textured superconductors

R. Gonzalez-Arrabal, M. Eisterer, H. W. Weber, G. Fuchs, P. Verges, and G. Krabbes

Appl. Phys. Lett. 81, 868 (2002); http://dx.doi.org/10.1063/1.1497705 (3 pages) | Cited 9 times

Online Publication Date: 22 July 2002

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We report on very high trapped fields (13.3 T at 33 K) achieved in bulk YBa2Cu3O7−δ melt-textured monoliths, which were reinforced by steel tubes to compensate the tensile stress generated during activation. The flux pinning properties were improved by neutron irradiation. The resulting increase of the critical current density shifts the maximum attainable trapped fields to higher temperatures (by about 10 K). © 2002 American Institute of Physics.
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74.72.-h Cuprate superconductors
61.80.Hg Neutron radiation effects
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.25.Sv Critical currents
74.62.Dh Effects of crystal defects, doping and substitution

Surface-modified GaAs terahertz plasmon emitter

J. Darmo, G. Strasser, T. Müller, R. Bratschitsch, and K. Unterrainer

Appl. Phys. Lett. 81, 871 (2002); http://dx.doi.org/10.1063/1.1497192 (3 pages) | Cited 9 times

Online Publication Date: 22 July 2002

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We studied the THz emission from n-GaAs plasmon emitters modified by low-temperature-grown (LT) GaAs surface layers. The THz emission is increased since the LT GaAs pins the Fermi level at a midgap position, increasing the surface depletion field. For a THz emitter with a 70-nm-thick LT GaAs layer we observe without external fields a THz emission intensity of 140 nW. In addition, the long-term performance of the modified emitters is improved by the LT GaAs surface layer. © 2002 American Institute of Physics.
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07.57.Hm Infrared, submillimeter wave, microwave, and radiowave sources
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.20.At Surface states, band structure, electron density of states
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
81.65.Mq Oxidation

Intrinsic nanostructural domains: Possible origin of weaklinkless superconductivity in the quenched reaction product of Mg and amorphous B

S. Li, O. Prabhakar, T. T. Tan, C. Q. Sun, X. L. Wang, S. Soltanian, J. Horvat, and S. X. Dou

Appl. Phys. Lett. 81, 874 (2002); http://dx.doi.org/10.1063/1.1497712 (3 pages) | Cited 6 times

Online Publication Date: 22 July 2002

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Smooth modulation structure of Mg–B alloy in the quenched reaction product of Mg and amorphous B was studied. It indicates that the MgB2 formed possibly in spinodal decomposition, thus resulting in MgB2 nanodomains. It was found that the nanodomains with small angle boundaries of atomic-scale width were distributed within the subgrains that constitute the clusters in MgB2 grains. This nanostructural characteristic may be intrinsic in the quenched reaction product of Mg and amorphous B. It makes the nanodomain boundaries not act as barriers to the current percolation path, thus exhibiting no weak-link problem in the MgB2. © 2002 American Institute of Physics.
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74.72.-h Cuprate superconductors
74.62.Dh Effects of crystal defects, doping and substitution
74.20.Mn Nonconventional mechanisms
61.46.-w Structure of nanoscale materials
74.25.F- Transport properties
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