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28 Jan 2002

Volume 80, Issue 4, pp. 535-701

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Advanced laminated antiferromagnetically coupled recording media with high thermal stability

S. I. Pang, S. N. Piramanayagam, and J. P. Wang

Appl. Phys. Lett. 80, 616 (2002); http://dx.doi.org/10.1063/1.1436281 (3 pages) | Cited 10 times

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A layered structure to improve the antiferromagnetic exchange coupling constant (J) in laminated antiferromagnetically coupled (LAC) media is proposed. This structure has a much larger thermal stability in comparison to simple LAC structures. It also improves the coercivity and decreases the remnant moment-thickness product to achieve a high resolution and a low pulse width. The recording measurements indicate that this structure has a slightly larger noise than the simple LAC structures. However, its overall signal-to-noise ratio (SNR) is comparable to that of the simple LAC structures. High SNR and much higher thermal stability make this structure suitable for ultrahigh areal densities. © 2002 American Institute of Physics.
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75.50.Ss Magnetic recording materials
85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
68.60.Dv Thermal stability; thermal effects
75.30.Et Exchange and superexchange interactions
75.50.Gg Ferrimagnetics
75.50.Vv High coercivity materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Irreversibility field and superconducting screening currents in EuBa2Cu3O7 films

K. Senapati, Leena K. Sahoo, N. K. Pandey, and R. C. Budhani

Appl. Phys. Lett. 80, 619 (2002); http://dx.doi.org/10.1063/1.1436525 (3 pages) | Cited 7 times

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Measurements of the critical current density (Jc) and irreversibility field [Birr(T)] of epitaxial, c-axis-oriented EuBa2Cu3O7 (Eu-123) films are reported. The transition temperature (Tc), Jc, and Birr(T) of these pulsed-laser-deposited films depend critically on the growth temperature (TD), growth rate (Gr), and the oxygen partial pressure (pO2) during growth. As compared to YBa2Cu3O7, Eu-based films require lower Gr, higher pO2, and higher TD. These differences are attributed to the lower adatom mobility of Eu and its propensity for a 2+ oxidation state. The lattice mismatch between (100) LaAlO3 and the ab-plane of Eu-123 leads to an elongated c axis and some randomly oriented islands whose growth is truncated by epitaxial lateral overgrowth as the film thickness increases. © 2002 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
74.25.Sv Critical currents
74.10.+v Occurrence, potential candidates

Epitaxial growth and valence control of strained perovskite SrFeO3 films

Hiroyuki Yamada, M. Kawasaki, and Y. Tokura

Appl. Phys. Lett. 80, 622 (2002); http://dx.doi.org/10.1063/1.1445805 (3 pages) | Cited 14 times

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We have fabricated single-crystalline thin films of perovskite-type iron oxide SrFeO3 which include high valent iron (Fe4+). The fabrication is accomplished on the lattice-mismatched substrates of SrTiO3 [(STO), 1.4% tensile strain] and (LaAlO3)0.3(SrAl0.5Ta0.5O3)0.7 [(LSAT), 0.5% tensile strain] by pulsed-laser deposition of SrFeO2.5 with Fe3+ state and subsequent annealing in ozone. The SrFeO2.5 films are grown in a layer-by-layer mode, exhibiting atomically smooth surfaces. The ozone annealed films on LSAT show metallic conductivity as observed in bulk SrFeO3, whereas those on STO remain semiconducting due to large tensile strain. A pseudomorphically strained epitaxial structure can be maintained by the proper choice of substrates and growth conditions through the huge volume change accompanied by the valence change from Fe3+ to Fe4+. © 2002 American Institute of Physics.
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81.15.Fg Pulsed laser ablation deposition
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.A- Nucleation and growth
61.72.Cc Kinetics of defect formation and annealing

Large magnetoresistance using hybrid spin filter devices

P. LeClair, J. K. Ha, H. J. M. Swagten, J. T. Kohlhepp, C. H. van de Vin, and W. J. M. de Jonge

Appl. Phys. Lett. 80, 625 (2002); http://dx.doi.org/10.1063/1.1436284 (3 pages) | Cited 88 times

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A magnetic “spin filter” tunnel barrier, sandwiched between a nonmagnetic metal and a magnetic metal, is used to create a magnetoresistive tunnel device, somewhat analogous to an optical polarizer-analyzer configuration. The resistance of these trilayer structures depends on the relative magnetization orientation of the spin filter and the ferromagnetic electrode. The spin filtering in this configuration yields a previously unobserved magnetoresistance effect, exceeding 100%. © 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.
75.47.De Giant magnetoresistance
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Enhanced low-field magnetoresistance in La2/3Ca1/3MnO3/Pr2/3Ca1/3MnO3 superlattices

H. Li, J. R. Sun, and H. K. Wong

Appl. Phys. Lett. 80, 628 (2002); http://dx.doi.org/10.1063/1.1445802 (3 pages) | Cited 22 times

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We report on the observation of enhanced low-field magnetoresistance in La2/3Ca1/3MnO3/Pr2/3Ca1/3MnO3 (LCMO/PCMO) superlattices with ultrathin PCMO layers. In particular, [LCMO(100 Å)/PCMO(10 Å)]17 superlattice exhibits magnetoresistance MR = Δρ/ρ0 = −55% in a magnetic field of 500 Oe and at temperature 219 K. The enhancement is associated with the ultrasharp metal–insulator transition. © 2002 American Institute of Physics.
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75.47.De Giant magnetoresistance
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
72.15.Gd Galvanomagnetic and other magnetotransport effects
75.50.Dd Nonmetallic ferromagnetic materials
72.60.+g Mixed conductivity and conductivity transitions

Magnetic coupling and magnetoresistance in Fe/Si1−xAgx multilayers

Hai Wang, Yunjun Tang, Xiang Li, Xi Chen, Yinjun Wang, Tao Zhu, Hongwu Zhao, and Wenshan Zhan

Appl. Phys. Lett. 80, 631 (2002); http://dx.doi.org/10.1063/1.1445466 (3 pages)

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In this letter, we present a study on the magnetic coupling and magnetoresistance (MR) properties in Fe/Si1−xAgx multilayers (MLs) with a granular Si1−xAgx spacer layer. We found that with increasing silver content (x) in a silicon matrix, the magnetic state of MLs varies from a nonmagnetic-coupling state to a weak-antiferromagnetic state around the percolation point of the ∼24-Å-thick granular spacer Si1−xAgx. The MR measurements also reveal an abrupt increase of MR near the same percolation point. These variations are ascribed to the formation of the percolation path in the granular spacer. © 2002 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.47.De Giant magnetoresistance

Magnetic properties and shape memory of Fe-doped Ni52Mn24Ga24 single crystals

G. H. Wu, W. H. Wang, J. L. Chen, L. Ao, Z. H. Liu, W. S. Zhan, T. Liang, and H. B. Xu

Appl. Phys. Lett. 80, 634 (2002); http://dx.doi.org/10.1063/1.1447003 (3 pages) | Cited 30 times

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Single crystals of a pseudoquaternary Heusler alloy, Ni52Mn16Fe8Ga24, have now been synthesized. The substitution of Fe for Mn strengthens the magnetic exchange interactions, increasing the Curie temperature to 381 K. The Fe also increases the Ni magnetic moment to 0.41 μB relative to that in the stoichiometric Heusler composition. The strain accompanying the martensitic transformation is 2.4% in zero field and can be enhanced to 4.2% by a field of 1.2 T. A field-induced strain of 1.15% has been induced along [001] in unstressed crystals with magnetic fields of 1.2 T applied at 291 K. © 2002 American Institute of Physics.
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75.30.Cr Saturation moments and magnetic susceptibilities
62.20.F- Deformation and plasticity
75.40.-s Critical-point effects, specific heats, short-range order
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.30.Et Exchange and superexchange interactions
81.40.Lm Deformation, plasticity, and creep
81.30.Kf Martensitic transformations
64.70.K- Solid-solid transitions
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