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1 Oct 2000

Volume 88, Issue 7, pp. 3795-4457

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Dynamics of fluxons in narrow window junctions

N. Flytzanis, N. Lazarides, A. Chiginev, V. Kurin, and J. G. Caputo

J. Appl. Phys. 88, 4201 (2000); http://dx.doi.org/10.1063/1.1289229 (11 pages) | Cited 9 times

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We numerically investigate the dynamics of a long window junction under the influence of a constant current bias, and intermediate damping in the junction area. The current voltage characteristics are calculated for various sizes of the passive region extension w′ and different thickness of the isolating layer in the idle region. The existence of the idle region influences the fluxon solutions, and consequently the I–V characteristics, causing the fluxons to increase their critical velocity above the Swihart velocity in the window and to radiate by way of the Cherenkov effect as they move in the junction. The fluxons become phase locked with the Cherenkov radiation, and this is reflected in the I–V curve as very strong resonances at relatively high velocities. © 2000 American Institute of Physics.
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74.50.+r Tunneling phenomena; Josephson effects
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)

Interface contribution to giant magnetoresistance in granular AgFe studied with Mössbauer spectroscopy

C. Alof, B. Stahl, M. Ghafari, and H. Hahn

J. Appl. Phys. 88, 4212 (2000); http://dx.doi.org/10.1063/1.1289232 (4 pages) | Cited 7 times

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The magnetotransport properties of granular thin AgFe films, prepared by codeposition of the constituent metals in an ultrahigh vacuum have been investigated. Mössbauer spectroscopy was employed to investigate the role of scattering of conduction electrons at the interface between the magnetic Fe particles and the Ag matrix. It is possible to determine the ratio of Fe atoms located at the Ag/Fe interface and in the particles (bulk atoms). The giant magnetoresistance effect correlates with the ratio of interface/bulk atoms. © 2000 American Institute of Physics.
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75.47.De Giant magnetoresistance
76.80.+y Mössbauer effect; other γ-ray spectroscopy
72.15.Gd Galvanomagnetic and other magnetotransport effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Magnetic domain structures and giant magnetoresistance of granular (Ni74Fe16Co10)35Ag65 films

H. Wang, X. Lu, X. Yan, S. P. Wong, W. Y. Cheung, N. Ke, J. B. Xu, S. J. Hu, D. C. Zeng, and Z. Y. Liu

J. Appl. Phys. 88, 4216 (2000); http://dx.doi.org/10.1063/1.1308063 (5 pages) | Cited 1 time

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In this article, granular (NiFeCo)35Ag65 films having a nominal atomic ratio of Ni:Fe:Co=74:16:10, near the zero magnetostriction ternary alloy, were prepared by dc magnetron co-sputtering. Subsequent thermal annealing was performed in a vacuum (<2×10−3 Pa) furnace for 1 h at various temperatures ranging from 250 to 500 °C. The crystalline structure and magnetic structure of the as-deposited and annealed films were characterized by Rutherford backscattering spectroscopy, x-ray diffraction, atomic force microscopy, and magnetic force microscopy. The giant magnetoresistance (GMR) for the films was measured as a function of temperature between 20 and 300 K using a conventional four-point probe dc technique in the presence of a magnetic field up to 7.6 kOe. It was found that, the crystalline structure, the magnetic structure, and consequently the GMR were closely related to the thermal treatment. The film annealed at the temperature of 300 °C has the isolated single domain structure and the highest GMR value of 19.1% at 20 K, while the film annealed at 500 °C has the long-range domain structure and the lowest GMR value of 9.9% at 20 K. © 2000 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.47.De Giant magnetoresistance
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.80.+q Magnetomechanical effects, magnetostriction
81.15.Cd Deposition by sputtering
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis

Micromagnetism and high temperature coercivity of MnBi/Al multilayers

U. Rüdiger, G. Güntherodt, P. Fumagalli, L. Thomas, S. S. P. Parkin, and A. D. Kent

J. Appl. Phys. 88, 4221 (2000); http://dx.doi.org/10.1063/1.1290466 (5 pages) | Cited 5 times

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The micromagnetic properties of multilayered MnBi/Al films have been investigated and compared to pure MnBi thin films. Pure MnBi films reveal an anomalous increase of the high temperature coercivity, which has been explained on the basis of a hybrid domain wall pinning model. The multilayer-type preparation of MnBi/Al thin films results in significantly reduced MnBi particle size of approximately 40 nm. The smaller particle size leads to a change of the dominant magnetization reversal process from one driven by domain wall movement toward coherent rotation. This was investigated via magnetic force microscopy imaging and micromagnetic calculations. The absence of domain walls during magnetization reversal results in a clear suppression of the increase of the high temperature coercivity observed in pure MnBi films. © 2000 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
81.05.Bx Metals, semimetals, and alloys
75.50.Cc Other ferromagnetic metals and alloys
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Crystallographic transformations of rapidly quenched Nd10Fe90−xTix

M. H. Yu, Z. D. Zhang, Q. F. Xiao, D. Y. Geng, W. Liu, and X. G. Zhao

J. Appl. Phys. 88, 4226 (2000); http://dx.doi.org/10.1063/1.1290736 (6 pages) | Cited 3 times

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The structural transformations from amorphous, metastable-to-equilibrium phases during annealing treatment of rapidly quenched Nd10Fe90−xTix (x=0, 2, 4, 6, 8, and 10) alloys have been studied systematically. By means of ac initial susceptibility and x-ray diffraction, a CaCu5-type metastable phase was observed for 0⩽x⩽10 as the crystallization of the amorphous alloys occurs below 700 °C. The CaCu5-type structure transforms into a TbCu7-type one with increasing the annealing temperature (above 700 °C). These melt-spun alloys have different structures including Th2Zn17 type for 0⩽x⩽4 and TbCu7 and ThMn12 types for 6⩽x⩽10, when annealed at high temperature (above 1000 °C). Nitrogenation was carried out at 400 °C for 10 h. Both Nd(Fe,Ti)5 and its nitride are soft-magnetic phases, like Nd(Fe,Ti)7 and Nd2(Fe,Ti)17. © 2000 American Institute of Physics.
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64.70.K- Solid-solid transitions
61.72.Cc Kinetics of defect formation and annealing
75.50.Kj Amorphous and quasicrystalline magnetic materials
81.05.Bx Metals, semimetals, and alloys
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
75.30.Cr Saturation moments and magnetic susceptibilities
81.30.Fb Solidification
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation

Suppression of microwave magnetic envelope solitons by continuous wave magnetostatic wave signals

Mark M. Scott, Yuri K. Fetisov, Valeri T. Synogach, and Carl E. Patton

J. Appl. Phys. 88, 4232 (2000); http://dx.doi.org/10.1063/1.1308099 (4 pages) | Cited 4 times

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The influence of continuous wave (cw) magnetostatic wave signals on microwave magnetic envelope soliton pulse formation and propagation in magnetic films has been examined. Pulsed and cw microwave signals were applied to the input of a single crystal yttrium–iron–garnet film magnetostatic wave delay line. The nominal operating frequency was 4.8 GHz. The pulse signals served to form solitons with no cw power present. Under suitable conditions, the cw signal served to inhibit or eliminate the soliton formation and propagation. The suppression effect was measured as a function of the cw signal frequency and power. The suppression is maximized when the cw signal frequency coincides with the pulse carrier frequency. At this frequency, an input cw power of 80 mW is sufficient to suppress completely a soliton pulse formed from a 10 ns wide, 500 mW peak power input pulse. © 2000 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Gg Ferrimagnetics
75.30.Ds Spin waves

Growth of ferromagnetic Nd0.7Sr0.3MnO3 films with an off-axis sputtering configuration

L. M. Wang, H. H. Sung, B. T. Su, H. C. Yang, and H. E. Horng

J. Appl. Phys. 88, 4236 (2000); http://dx.doi.org/10.1063/1.1289075 (5 pages) | Cited 14 times

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Ferromagnetic Nd0.7Sr0.3MnO3 (NSMO) films have been prepared onto (001) SrTiO3 by the off-axis magnetron sputtering technique. The NSMO films are characterized by resistivity measurements, x-ray diffraction, and the atomic force microscope. Under our deposition conditions the films show a maximum resistivity (ρmax) at the highest peak temperature of Tp=180–240 K. By increasing the deposition temperature, Tp shifts to lower temperature and ρmax increases. In an applied magnetic field, large magnetoresistance (MR) ratios >2200% for several in situ deposited films at 180 K and H=6 T are obtained. The influence of growth conditions on the magnetotransport properties of NSMO films and their MR characteristics are discussed. © 2000 American Institute of Physics.
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81.15.Cd Deposition by sputtering
75.50.Dd Nonmetallic ferromagnetic materials
75.70.Ak Magnetic properties of monolayers and thin films
75.47.Gk Colossal magnetoresistance
75.47.De Giant magnetoresistance
72.20.My Galvanomagnetic and other magnetotransport effects

Structure and magnetic properties of Gd3Fe28.2W0.8

Q. L. Liu, G. H. Rao, J. K. Liang, and B. G. Shen

J. Appl. Phys. 88, 4241 (2000); http://dx.doi.org/10.1063/1.1309035 (4 pages) | Cited 7 times

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The ternary intermetallic compound Gd3Fe28.2W0.8 with a Nd3Fe29−xTix-type structure was synthesized with W as a stabilizing element, and its crystal structure and magnetic properties were investigated by means of x-ray powder diffraction and magnetic measurements. The space group of Gd3Fe28.2W0.8 is A2/m with lattice parameters a=10.5812 Å, b=8.5338 Å, c=9.6986 Å, and β=96.86°. Rietveld refinement of the crystal structure reveals that W atoms occupy exclusively three crystallographic positions (4g, 4i3, 4i4) with only one neighboring Gd atom. The preferential occupation of W atoms can be understood in terms of the site volume and enthalpy of mixing. The compound exhibits a planar magnetocrystalline anisotropy perpendicular to the [102] direction. The Curie temperature Tc, saturation moment Ms, and anisotropy field HA are 502 K, 38.6 μB/f.u., and 7.5 T, respectively. © 2000 American Institute of Physics.
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75.50.Vv High coercivity materials
75.50.Cc Other ferromagnetic metals and alloys
75.30.Gw Magnetic anisotropy
61.66.Dk Alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
64.75.-g Phase equilibria

Magneto-optical spectra of excitons and Landau subbands in strained CdTe epitaxial films under high magnetic fields

K. Watanabe and N. Miura

J. Appl. Phys. 88, 4245 (2000); http://dx.doi.org/10.1063/1.1290464 (5 pages) | Cited 2 times

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High quality CdTe thin epitaxial films were grown on (100)-GaAs substrates by hot wall epitaxy. Doublet structures consisting of a heavy hole exciton and a light hole exciton were observed in reflection and absorption spectra. This splitting is caused by biaxial thermal strain. Magnetoreflection and magnetoabsorption spectra were measured in magnetic fields up to 40 T. It was found from the diamagnetic shift of the excitons that the hole effective masses are drastically changed from unstrained crystals. Interband transitions between Landau subbands were clearly observed in the magnetoabsorption spectra at strong magnetic fields. © 2000 American Institute of Physics.
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78.66.Hf II-VI semiconductors
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
78.20.Ls Magneto-optical effects
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Monte Carlo approach to phase transitions in ferroelectromagnets

X. S. Gao, J.-M. Liu, X. Y. Chen, and Z. G. Liu

J. Appl. Phys. 88, 4250 (2000); http://dx.doi.org/10.1063/1.1309053 (7 pages) | Cited 22 times

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A Monte Carlo algorithm based on the hybrid Ising-DIFFOUR model is proposed to investigate the phase transition in ferroelectromagnetic lattice in which the ferroelectric order and antiferromagnetic order coexist below a certain temperature. The Ising spin moment and ferroelectric displacement and their susceptibilities as well, as a function of temperature for systems of different magnetoelectric couplings, are simulated and compared with the mean-field approach. The typical antiferromagnetic transition at Néel point and the ferroelectric transition at Curie point are observed at zero coupling. It is demonstrated that a weak ferromagnetic order can be activated by introducing the magnetoelectric coupling or applying external magnetic field, while the external electric field has little effect on the ferromagnetic ordering behavior. © 2000 American Institute of Physics.
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75.10.Hk Classical spin models
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
77.80.B- Phase transitions and Curie point

Microstructure and magnetic properties of strained La0.7Sr0.3MnO3 thin films

A. M. Haghiri-Gosnet, J. Wolfman, B. Mercey, Ch. Simon, P. Lecoeur, M. Korzenski, M. Hervieu, R. Desfeux, and G. Baldinozzi

J. Appl. Phys. 88, 4257 (2000); http://dx.doi.org/10.1063/1.1309040 (8 pages) | Cited 57 times

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The lattice deformation of dense strained La0.7Sr0.3MnO3 (LSMO) films is shown to control the easy direction of the magnetization. Optimized pulsed laser deposited conditions allow the fabrication of dense LSMO thin films which present an exceptional flatness with a peak–valley roughness (Rp–v) of 1 Å, associated to epitaxial grains as large as 1 μm. Electron microscopy coupled with x-ray diffraction have been used to study the unit cell distortion of both tensile and compressive dense LSMO films as a function of the thickness. No relaxation of the lattice distortion imposed by substrate has been observed in the thickness range 10–60 nm. The Curie temperature is not significantly affected by the nature of the substrate: a TC of 350 K is observed for both SrTiO3 (STO) and LaAlO3 (LAO) substrates, i.e., close to the bulk material (369 K). In contrast, the easy direction of magnetization depends on the substrate. For tensile films deposited on the STO substrate, the unit cell is elongated along the film’s plane (ain-plane=3.905 Å) with a reduced perpendicular parameter (cperp=3.85 Å): an easy direction of magnetization M in the plane of the film is observed. For compressive films deposited on LAO substrate, the situation is reversed with a unit cell elongated along the direction of growth (cperp=4.00 Å and ain-plane=3.79 Å) and an easy axis for M along this perpendicular out-plane direction. It is thus demonstrated that the larger cell parameter, ain-plane for films deposited on STO and cperp for films deposited on LAO, is fully correlated to the direction of the easy magnetization. © 2000 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Dd Nonmetallic ferromagnetic materials
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
75.47.Gk Colossal magnetoresistance
75.47.De Giant magnetoresistance
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
81.15.Fg Pulsed laser ablation deposition

A semiquantitative analytic model for the magnetic response of a Terfenol-D impregnated composite specimen under tension

C. A. Feickert, J. Berman, J. Kamphaus, J. Trovillion, and R. Quattrone

J. Appl. Phys. 88, 4265 (2000); http://dx.doi.org/10.1063/1.1308101 (4 pages) | Cited 1 time

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Magnetostrictive composites have found increasing use as a tagging agent for structural integrity monitoring. A simple magnetic model based on Heisenberg–Weiss theory is put forth that provides guidance as to the physical parameters that govern the magnetic response of a Terfenol-D impregnated composite specimen in tension. Further, the model provides an effective analytic parameterization of the magnetic response, resulting from unidirectional tension, and affords estimates of these parameters. © 2000 American Institute of Physics.
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75.80.+q Magnetomechanical effects, magnetostriction
75.10.Jm Quantized spin models, including quantum spin frustration

Blastfurnace slag cements: A construction material with very unusual nuclear spin relaxation behavior during hardening

Nikolaus Nestle, Marwan Dakkouri, Oliver Geier, Dieter Freude, and Jörg Kärger

J. Appl. Phys. 88, 4269 (2000); http://dx.doi.org/10.1063/1.1288506 (5 pages) | Cited 11 times

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In this contribution, nuclear magnetic resonance (NMR) relaxometry results on hardening hydraulically activated blastfurnace slag pastes are presented. The results are found to be very different from the behavior of other hydraulic building materials such as cement and gypsum. A mechanism based on water diffusion in inner field gradients is suggested in order to explain the observed relaxation behavior and corroborated by additional experimental evidence from magnetic susceptibility measurements and NMR relaxation measurements on slag pastes prepared from nonwatery fluids. © 2000 American Institute of Physics.
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76.60.Es Relaxation effects
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