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11 Sep 2000

Volume 77, Issue 11, pp. 1569-1731

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Thickness-dependent transport properties of Nd2/3Sr1/3MnO3 thin films

A. Barman and G. Koren

Appl. Phys. Lett. 77, 1674 (2000); http://dx.doi.org/10.1063/1.1309028 (3 pages) | Cited 11 times

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A systematic study is reported on the thickness dependence of the electrical resistivity in thin films of the giant magnetoresistance manganite Nd2/3Sr1/3MnO3. We observed a first-order phase transition versus thickness in these films, which is seen as a jump of about 30 K in the metal-to-insulator transition temperature (Tp) at film thickness of 50–60 nm. This phenomenon is attributed to a sudden release of strain in the film as its thickness increases. We also observed at low temperatures, 5–30 K, another transition from localized-to-metallic behavior versus film thickness, which is also related to the strain relief in the films. © 2000 American Institute of Physics.
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75.47.De Giant magnetoresistance
73.61.Ng Insulators
71.30.+h Metal-insulator transitions and other electronic transitions
75.70.Ak Magnetic properties of monolayers and thin films

Flux trapping in a superconducting thin film as revealed by simulations and scanning superconducting quantum interference device microscope observations

Keiichi Tanaka, Toshimitsu Morooka, Akikazu Odawara, Kazuo Chinone, Yasunori Mawatari, and Masao Koyanagi

Appl. Phys. Lett. 77, 1677 (2000); http://dx.doi.org/10.1063/1.1310177 (3 pages) | Cited 2 times

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Penetration of magnetic fluxes into a superconducting thin film that contained holes was studied for fast and slow cooling rates (0.18 and 0.009 K/s, respectively) under an ambient magnetic field of about 3 μT. By using a scanning superconducting quantum interference device microscope, we observed trapped magnetic fluxes both inside and outside of holes prepared in a superconducting film. The trapped fluxes outside the holes appeared in a regular arrangement when the superconducting film was cooled at the slow rate. Observed arrangements of the trapped fluxes were compared with a simulation that was based on a theoretical model that considered the surface barrier and the interaction among fluxes. The simulation explained well the observed arrangements of magnetic fluxes. © 2000 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.25.Ha Magnetic properties including vortex structures and related phenomena

Dynamic nuclear polarization by spin injection

Mark Johnson

Appl. Phys. Lett. 77, 1680 (2000); http://dx.doi.org/10.1063/1.1310173 (3 pages) | Cited 8 times

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A theory is presented to describe quantitatively how nuclear spin polarization can be induced in a metal by a dc electric bias current driven through the sample. The bias current is spin polarized by passing through a thin ferromagnetic film in interfacial contact with the sample, with the polarization axis determined by the magnetization orientation of the ferromagnetic layer. The nuclear spins are polarized due to spin angular momentum transfer from the electrons to the nuclei mediated by the contact hyperfine interaction. Upon reversing the polarity of the bias current, the sign of the nuclear polarization is reversed. Unlike other methods of dynamic nuclear polarization, spin-injected dynamic nuclear polarization is a zero frequency technique that in principle does not require an applied magnetic field.
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76.70.Fz Double nuclear magnetic resonance (DNMR), dynamical nuclear polarization
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Magnetoresistance effect in the fluctuating-valence BaSmFe2O5+w system

J. Nakamura, J. Lindén, M. Karppinen, and H. Yamauchi

Appl. Phys. Lett. 77, 1683 (2000); http://dx.doi.org/10.1063/1.1310170 (3 pages) | Cited 10 times

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The occurrence of negative magnetoresistance (MR) in semiconductive BaSmFe2O5+w double-perovskite samples is demonstrated. A peak in the MR value was observed at the Verwey–type transition temperature. The transition signifies the charge separation of the Fe2.5+ fluctuating mixed valence state into high-spin Fe2+ and Fe3+. The samples were ferrimagnetic with a Curie temperature of ∼ 710 K. Upon oxidizing/reducing the samples the size of the MR peak and the temperature at which the peak occurred varied. The largest MR value observed was 1.4% at 7 T. © 2000 American Institute of Physics.
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72.20.My Galvanomagnetic and other magnetotransport effects
75.50.Pp Magnetic semiconductors
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Gg Ferrimagnetics
71.28.+d Narrow-band systems; intermediate-valence solids

Dependence of critical current on field angle in off-c-axis grown Bi2Sr2CaCu2O8 film

J. H. Durrell, G. Gibson, Z. H. Barber, J. E. Evetts, R. Rössler, J. D. Pedarnig, and D. Bäuerle

Appl. Phys. Lett. 77, 1686 (2000); http://dx.doi.org/10.1063/1.1310174 (3 pages) | Cited 6 times

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Critical current measurements for varying angles of applied field have been performed on Bi2Sr2CaCu2O8 thin films grown on 10° vicinal (001) substrates. Measurements were performed on current tracks orientated both parallel (L) and transverse (T) to the vicinal steps. No Josephson vortex channeling effect was observed, in contrast to results previously obtained on both oxygenated and deoxygenated YBa2Cu3O7−δ films grown on vicinal substrates. In addition, no force-free peak was observed when the applied field was parallel to the current. This provides experimental evidence that there is a difference between the pancake coupling mechanism in YBa2Cu3O7−δ at small field angles where Josephson vortices are present and that in Bi2Sr2CaCu2O8. © 2000 American Institute of Physics.
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74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
74.25.Sv Critical currents
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.50.+r Tunneling phenomena; Josephson effects

Determination of first and second magnetic anisotropy constants of magnetic recording media

Yasushi Endo, Osamu Kitakami, Satoshi Okamoto, and Yutaka Shimada

Appl. Phys. Lett. 77, 1689 (2000); http://dx.doi.org/10.1063/1.1310166 (3 pages) | Cited 16 times

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We propose a simple method to evaluate the first and second magnetic anisotropy constants of high-density magnetic recording media with their easy axis in the film plane. By measuring the magnetization curve along the film normal, uniaxial anisotropy constants K1 and K2 can be determined simultaneously. The present method has been applied to (11⋅0) oriented CoCrPtTa hard disk media. The measured anisotropy constants are presented along with their temperature dependence. We also point out serious shortcomings of the currently used evaluation methods, such as the rotational hysteresis method and the singular point detection technique, which usually overestimate the magnetic anisotropy constant. © 2000 American Institute of Physics.
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75.30.Gw Magnetic anisotropy
75.50.Ss Magnetic recording materials
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Edge-pinned states in patterned submicron NiFeCo structures

Jing Shi and S. Tehrani

Appl. Phys. Lett. 77, 1692 (2000); http://dx.doi.org/10.1063/1.1290599 (3 pages) | Cited 23 times

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Magnetization reversal in patterned submicron NiFeCo structures has been studied. Application of a transverse field lowers the easy axis switching threshold of the center of the structures but the edge magnetization remains pinned along the initial direction until a higher reversal field is applied. Complete switching between the two stable magnetization states occurs only after depinning and reversal of the edge magnetization. The edge depinning field is found to be very insensitive to the transverse field strength. Micromagnetic simulations are used to characterize the magnetization reversal process. © 2000 American Institute of Physics.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Bb Fe and its alloys
75.40.Mg Numerical simulation studies
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