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1 Mar 2004

Volume 84, Issue 9, pp. 1435-1613

Issue Cover Spotlight Figure

Appl. Phys. Lett. 84, 1558 (2004); http://dx.doi.org/10.1063/1.1651641 (3 pages)

DongWeon Lee, Adrian Wetzel, Roland Bennewitz, Ernst Meyer, Michel Despont, Peter Vettiger, and Christoph Gerber
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Switching current versus magnetoresistance in magnetic multilayer nanopillars

S. Urazhdin, Norman O. Birge, W. P. Pratt, and J. Bass

Appl. Phys. Lett. 84, 1516 (2004); http://dx.doi.org/10.1063/1.1651645 (3 pages) | Cited 53 times

Online Publication Date: 25 February 2004

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We study current-driven magnetization switching in nanofabricated magnetic trilayers, varying the magnetoresistance in three different ways. First, we insert a strongly spin-scattering layer between the magnetic trilayer and one of the electrodes, giving increased magnetoresistance. Second, we insert a spacer with a short spin-diffusion length between the magnetic layers, decreasing the magnetoresistance. Third, we vary the angle between layer magnetizations. In all cases, we find an approximately linear dependence between magnetoresistance and inverse switching current. We give a qualitative explanation for the observed behaviors, and suggest some ways in which the switching currents may be reduced. © 2004 American Institute of Physics.
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68.65.Ac Multilayers
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
72.15.Qm Scattering mechanisms and Kondo effect
75.50.Bb Fe and its alloys

Writing and reading bits on pre-patterned media

J. Moritz, L. Buda, B. Dieny, J. P. Nozières, R. J. M. van de Veerdonk, T. M. Crawford, and D. Weller

Appl. Phys. Lett. 84, 1519 (2004); http://dx.doi.org/10.1063/1.1644341 (3 pages) | Cited 32 times

Online Publication Date: 25 February 2004

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We have written and read back bits on perpendicular pre-patterned media prepared by electron-beam lithography. Using a contact tester equipped with a standard longitudinal head, we are able to write different bit lengths on 100×200 nm2 dots spaced 100 nm apart. These tests demonstrate the role played by the distribution of the coercive fields of the dots during the write process. Signal-to-noise ratios (SNRs) are obtained by numerical analysis and are found to be on the same order of magnitude as in continuous perpendicular media, but remain constant at decreasing bit lengths. This property of the SNR is due to a partial reduction of transition noise. The potential to pattern these media with nanoimprint lithography and their good recording performance make them candidates for ultrahigh density recording. © 2004 American Institute of Physics.
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85.40.Hp Lithography, masks and pattern transfer

Inhomogeneous magnetization of a superconducting film measured with a gradiometer

H. Stalzer, A. Cosceev, C. Sürgers, H. v. Löhneysen, J.-M. Brosi, G.-A. Chakam, and W. Freude

Appl. Phys. Lett. 84, 1522 (2004); http://dx.doi.org/10.1063/1.1655706 (3 pages) | Cited 2 times

Online Publication Date: 25 February 2004

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The magnetic flux generated by the screening currents of a superconducting Nb film in the Meissner state is measured with a coaxial gradiometer in a weak magnetic field B. A peculiar position dependence is found when the sample surface is only slightly tilted away from the parallel field orientation and shifted with respect to the center axis of the gradiometer. This is due to the inhomogeneous magnetization with a strong out-of-plane contribution measured by the two pick-up coils as confirmed by numerical finite-element calculations. The unusual position dependence has important consequences for interpreting the diamagnetic screening of superconducting films measured by a coaxial gradiometer near the parallel-field orientation. © 2004 American Institute of Physics.
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74.25.Ha Magnetic properties including vortex structures and related phenomena
74.78.-w Superconducting films and low-dimensional structures
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems

Nanotube magnetism

Y. C. Sui, R. Skomski, K. D. Sorge, and D. J. Sellmyer

Appl. Phys. Lett. 84, 1525 (2004); http://dx.doi.org/10.1063/1.1655692 (3 pages) | Cited 68 times

Online Publication Date: 25 February 2004

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FePt and Fe3O4 nanotubes are produced by hydrogen reduction in nanochannels of porous alumina templates and investigated by electron microscopy, x-ray diffraction analysis, and magnetic measurements. Loading the templates with a Fe chloride and Pt chloride mixture followed by hydrogen reduction at 560 °C leads to the formation of ferromagnetic FePt nanotubes in the alumina pores. Using a Fe nitrate solution, thermally decomposed at 250 °C and reduced in hydrogen for 2.5 h at the same temperature, yields Fe3O4 tubes. The length of the nanotubes is about 50 μm and their diameters range from about 150 to 220 nm, depending on the thickness of the template film and the pore diameter distribution. Reflecting the different magnetocrystalline anisotropies of the compounds, the coercivities range from 0.61 kOe for Fe3O4 to 20.9 kOe for FePt. The hysteresis is explained in terms of a tubular random-anisotropy model, which yields a diameter and anisotropy dependent transition from a curling-type mode (Fe3O4) to a localized mode (FePt). © 2004 American Institute of Physics.
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75.50.Bb Fe and its alloys
75.50.Dd Nonmetallic ferromagnetic materials
61.46.-w Structure of nanoscale materials
75.50.Tt Fine-particle systems; nanocrystalline materials
81.05.Cy Elemental semiconductors
75.30.Gw Magnetic anisotropy
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
75.70.Rf Surface magnetism
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Effects of magnetic field on the manganite-based bilayer junction

J. R. Sun, C. M. Xiong, T. Y. Zhao, S. Y. Zhang, Y. F. Chen, and B. G. Shen

Appl. Phys. Lett. 84, 1528 (2004); http://dx.doi.org/10.1063/1.1664032 (3 pages) | Cited 81 times

Online Publication Date: 25 February 2004

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An oxide bilayer junction has been fabricated by growing a La0.32Pr0.35Ca0.33MnO3 film on 0.5 wt % Nb-doped SrTiO3 crystal, and its behavior under magnetic field is experimentally studied. It is found that external field greatly affected the rectifying property and the resistance of the junction, causing an extremely large magnetoresistance. The most striking observation of the present work is that the magnetoresistance of the junction can be either positive or negative, depending on temperature and applied current, and is asymmetric with respect to the direction of the bias current. These results reveal the great potential of the manganites in configuring artificial devices. © 2004 American Institute of Physics.
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75.50.Dd Nonmetallic ferromagnetic materials
72.20.My Galvanomagnetic and other magnetotransport effects
75.47.Lx Magnetic oxides
71.20.Ps Other inorganic compounds
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