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4 Sep 2000

Volume 77, Issue 10, pp. 1413-1560

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Giant magnetostriction in an ordered Fe3Pt single crystal exhibiting a martensitic transformation

Tomoyuki Kakeshita, Tetsuya Takeuchi, Takashi Fukuda, Masato Tsujiguchi, Toshio Saburi, Ryuichiro Oshima, and Shunsuke Muto

Appl. Phys. Lett. 77, 1502 (2000); http://dx.doi.org/10.1063/1.1290694 (3 pages) | Cited 112 times

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Magnetostriction measurements have been made in an ordered Fe3Pt single crystal with degree of order of about 0.8, which exhibits a cubic-tetragonal martensitic transformation at 97 K. The specimen was cooled down to 4.2 K without magnetic field, and then a magnetic field of 4 T is applied to the specimen along 〈001〉 at 4.2 K and removed. As a result, a reversible giant magnetostriction of about 0.5% is observed. This reversible magnetostriction will be caused by the rearrangement of crystallographic domains, being three times as large as that of Terfenol-D (Fe2DyxTb1−x: typical magnetostrictive materials). © 2000 American Institute of Physics.
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75.80.+q Magnetomechanical effects, magnetostriction
64.70.K- Solid-solid transitions
75.60.Ch Domain walls and domain structure
75.50.Bb Fe and its alloys
81.30.Kf Martensitic transformations

Determination of average demagnetizing fields in longitudinal magnetic recording using nanosecond field pulses

A. Moser, D. Weller, N. D. Rizzo, and T. J. Silva

Appl. Phys. Lett. 77, 1505 (2000); http://dx.doi.org/10.1063/1.1290688 (3 pages) | Cited 3 times

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The demagnetizing field across bit transitions in longitudinal recording media is measured quantitatively as a function of linear density using a quasi static write/read tester. Bit transitions with varying linear densities in the range 500–6000 flux changes per mm are recorded on CoCr10Ta4 media films. The media are deposited onto a coplanar waveguide structure, which is used to generate reversal field pulses of well-defined amplitude and 10 ns width to minimize thermally activated processes. The demagnetizing field is extracted from the measured reversal field, which is the sum of the external waveguide field and the internal, density-dependent demagnetizing field. The experimental results are qualitatively consistent with those predicted by a simple magnetostatic model that assumes finite transition widths. © 2000 American Institute of Physics.
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75.50.Ss Magnetic recording materials
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Cc Other ferromagnetic metals and alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Magnetotunneling in sputtered La0.7Ca0.3MnO3/Al2O3 multilayers

Y. Luo, A. Käufler, and K. Samwer

Appl. Phys. Lett. 77, 1508 (2000); http://dx.doi.org/10.1063/1.1290718 (3 pages) | Cited 14 times

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Magnetic multilayers in the form of [La0.7Ca0.3MnO3/Al2O3]n+La0.7Ca0.3MnO3 were sputtered to study their magnetotunneling effect. Structural analyses were performed by standard x-ray scattering, showing a well-defined superlattice. Both current perpendicular to plane (CPP) and current in plane (CIP) methods were applied for the magnetoresistance measurements. The CPP value gives the tunneling effect through the thin insulating layers and shows a large low-field effect of about 60% for the trilayer junction and 50% for the superlattice structure at 5 K, respectively. The CIP effect is about 30% (5 K) for all samples and is dominated here by the contribution of the intergrain tunneling effect within the La0.7Ca0.3MnO3 layers. © 2000 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.45.+j Macroscopic quantum phenomena in magnetic systems
73.61.Ng Insulators

Scanning aperture photoemission microscopy for magnetic imaging

Gary M. McClelland and Charles T. Rettner

Appl. Phys. Lett. 77, 1511 (2000); http://dx.doi.org/10.1063/1.1290721 (3 pages)

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Magnetic imaging has been demonstrated by photoemission microscopy in which spatial resolution is achieved by scanning an aperture across the sample. To achieve magnetic contrast, the difference between photoemission current with right and left circularly polarized light is recorded while holding the aperture-surface distance to 30 nm. We used conical gold tips with apertures as small as 30 nm, drilled by a focused ion beam. Images of Co/Pt multilayer films show a magnetic contrast of ±2% and a resolution (25%–75% of a step) of 30 nm. Resolution better than 10 nm should be achievable with smaller apertures. With this imaging method, there is no magnetic interaction between sample and tip, and ultrafast time resolution should be achievable. © 2000 American Institute of Physics.
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07.55.-w Magnetic instruments and components
07.79.-v Scanning probe microscopes and components
79.60.-i Photoemission and photoelectron spectra
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Sm–Co–Cu–Ti high-temperature permanent magnets

J. Zhou, R. Skomski, C. Chen, G. C. Hadjipanayis, and D. J. Sellmyer

Appl. Phys. Lett. 77, 1514 (2000); http://dx.doi.org/10.1063/1.1290719 (3 pages) | Cited 72 times

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A class of promising permanent-magnet materials with an appreciable high-temperature coercivity of 8.6 kOe at 500 °C is reported. The Sm–Co–Cu–Ti magnets are prepared by arc melting and require a suitable heat treatment. Magnetization measurements as a function of temperature and x-ray diffraction patterns indicate that the samples are two-phase mixtures of 2:17 and 1:5 structures. Depending on heat treatment and composition, some of the magnets exhibit a positive temperature coefficient of coercivity. The promising high-temperature behavior of the coercivity is ascribed to the temperature dependence of the domain-wall energy, which affects the curvature of the walls and the pinning behavior. © 2000 American Institute of Physics.
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75.50.Ww Permanent magnets
75.50.Cc Other ferromagnetic metals and alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.40.Rs Electrical and magnetic properties related to treatment conditions
81.40.Gh Other heat and thermomechanical treatments
75.60.Ch Domain walls and domain structure

Anomalous magnetotransport in Pr0.5Ca0.5Mn0.99Cr0.01O3

R. Mahendiran, A. Maignan, M. Hervieu, C. Martin, and B. Raveau

Appl. Phys. Lett. 77, 1517 (2000); http://dx.doi.org/10.1063/1.1290726 (3 pages) | Cited 7 times

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Pr0.5Ca0.5Mn0.99Cr0.01O3 shows several anomalous properties: Field-cooled (FC) resistivity at 10 K is several orders of magnitude lower than the zero-field cooled (ZFC) value, magnetoresistance isotherm at 125 K is asymmetric about the origin (H = 0 T) and resistivity and magnetization are hysteretic between field cooling and field warming. No clear difference between ZFC and FC magnetization up to 5 T was found. We suggest that nanometric-size ferromagnetic clusters coexist with the charge-ordered antiferromagnetic matrix in H = 0 T and the matrix breaks into domains upon field cooling which leads to low resistivity. © 2000 American Institute of Physics.
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75.47.Gk Colossal magnetoresistance
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
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