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1

Digitale Medien

Localization and hopping of magnetoelastic waves in highly magnetostrictive strings with random chain structures (abstract) : The 41st annual conference on magnetism and magnetic materials (1997)

Inoue, M. ; Nishimura, K. ; Fujii, T.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 81 (1997), S. 5692-5692

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Analogous to the localization of the wave function of an electron in a random potential (Anderson localization), in the macroscopic system of magnetoelastic waves (MEWs) propagating in a highly magnetostrictive string exhibiting the giant ΔE effect, the piling-up of MEWs into a wave-packet in a restricted small region of the string is expected. This wave-packet is subject to hopping in a discontinuous wave by applying a magnetic field due to the change in the local elastic states caused by the ΔE effect. From this expectation, a theoretical analysis was performed focusing on the derivation of localization conditions of MEWs. The analysis was carried out using a one-dimensional string model having high magnetostriction. The string is assumed to be composed of random chains with (1) alloy-type disorder (random weights of masses with equal spacings) and (2) liquid-type disorder (random spacings of masses with equal weights). For the elastic and magnetoelastic constants of the string, the value of Fe78Si10B12 amorphous wire (Unitika) were used in the calculations. No substantial changes in the localization states were not recognized in both modes. The analysis revealed that, when the change of the apparent Young's modulus with magnetic field ΔE is 28%, the localized MEWs are subject to hopping conserving their wave identities (eigenfrequencies and eigenstates). This result in considered to originate from the changes in the disorder conditions to support the localization of MEWs. To confirm the above theoretical prediction experimentally, MEW properties have been measured by using Fe78Si10B12 amorphous wires connecting weights made of leads to form the random chain structure. The localized MEWs are, indeed, observed by detecting the local vibrations of the wires. Theoretical and experimental results will be presented in detail at the conference. © 1997 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.364639

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2

Digitale Medien

Measurements of charged particles in the laser ablation plume of polymers (1995)

Fujii, T. ; Inoue, S. ; Kannari, F.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 78 (1995), S. 3401-3407

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Charged particles in organic polymer plumes photoablated by ultraviolet lasers are measured with a Faraday cup assembly. In spite of a relatively low F2 laser (157 nm) fluence 〈1 J/cm2, relative charged fragment concentrations measured for polyimide, polytetrafluoroethylene, and polyethyleneterephthalate targets are (approximately-greater-than)10−3. Charged particle concentrations in the ablation plumes generated by an F2 laser with polyethyleneterephthalate and polyimide targets are always higher than those in KrF laser (248 nm) ablation plumes at the same specific laser energy deposited on the target. Charged fragments have also higher velocities in the F2 laser ablation plumes. An exponential increase in the charged fragment concentration with increasing laser fluence suggests that the ions are mainly produced through electron-neutral collisions in the hot material core close to the target surface. © 1995 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.359968

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3

Digitale Medien

Free-carrier lifetime and deep-level luminescence in semi-insulating GaAs: The influence of indium doping and growth in a magnetic field (1989)

Leo, K. ; Rühle, W. W. ; Nordberg, P. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 66 (1989), S. 1800-1804

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The influence of In doping and/or of growth in a magnetic field on the properties of Czochralski-grown semi-insulating GaAs wafers is investigated. We determine the spatial distribution of the free-carrier lifetime by time-resolved luminescence in the ps regime. The results are compared with the spatial distribution of the near-band-edge and deep-level luminescence. The macroscopical and microscopical homogeneity of the carrier lifetime and the luminescence intensities are improved by the growth in a magnetic field. Indium doping leads to similar improvements and additionally to an increase of the absolute value of the lifetime. The combination of In doping and growth in a magnetic field gives the best results.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.344351

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4

Digitale Medien

Fabrication of transparent iron-oxide films by means of sol-gel synthesis (abstract) (1988)

Yamaguchi, K. ; Fujii, T. ; Kuranouchi, S. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 64 (1988), S. 5452-5452

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Transparent iron-oxide films were fabricated by sol-gel synthesis using a solution of ferric nitrate (III) dissolved in ethylene glycol.1 The solution was kept at 80 °C and stirred constantly in a nitrogen atmosphere. The gel with an appropriate viscosity was spin coated on soft glass plates, then dried and heated in air at various temperatures for 5 h. The films thus prepared are about 0.2 μm thick, amber colored, and especially transparent in the near-infrared region, whose transmittance exceeds 90%. Maximum saturation magnetization 4πMs=0.74 kG [curve (a)] was obtained by annealing at 450 °C, which is still insufficient to use practical application. Reduction heat treatment in a hydrogen atmosphere is found to be very effective to improve magnetic properties: 4πMs is increased to 3 kG [curve (b)], which is about four times as large as the previous one, but the films become semitransparent due to formation of magnetite particles. Original high transmittance recovers by successive annealing in air at 400 °C without any degradation of magnetic properties [curve (c)], where diffraction peaks of maghemite were observed. This strongly suggests that magnetic anisotropy may be arbitrarily controlled by forming linear chains of ferromagnetic particle clusters through reduction heat treatment in a magnetic field. Faraday rotation θF of the samples was also measured. These films are promising as a new type magneto-optic material.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.342345

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5

Digitale Medien

Preparation and characterization of (111)-oriented Fe3O4 films deposited on sapphire (1989)

Fujii, T. ; Takano, M. ; Katano, R. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 66 (1989), S. 3168-3172

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Films of various iron oxides including FeO, Fe3 O4 , and α-Fe2 O3 were formed on the α-Al2 O3 (0001) surface by a reactive vapor deposition method and characterized by x-ray diffraction and conversion electron Mössbauer spectroscopy (CEMS). The formation range for each phase was determined as a function of the substrate temperature (Ts ) and oxygen partial pressure (PO2 ). Typically, the deposition of (111)-oriented epitaxial magnetite films could be performed at low temperatures of Ts =523∼623 K and PO2 =1.0–5.0×10−4 Torr. Good stoichiometry of the as-grown films were confirmed by CEMS, and the Verwey transition was clearly detected by measurements of resistivity and CEMS down to 77 K. However, the large lattice mismatch between the substrate and Fe3 O4 resulted in a columnar particle growth. The initially grown phase on such a mismatched substrate was specifically characterized by depositing the Mössbauer active isotope, 57 Fe, only at the deepest layers. On the other hand, by depositing 57 Fe only in the topmost layers, surface layers of well-crystallized films have been found to be rather stable against oxidation.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.344154

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6

Digitale Medien

Study of Au-n-type GaAs Schottky contacts on a single-crystal part of large-grained polycrystalline GaAs (1986)

Hattori, K. ; Ohtani, T. ; Fujii, T.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 59 (1986), S. 2507-2510

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Gold-n-type GaAs Schottky contacts have been fabricated on a single-crystal part of polycrystalline GaAs with grain size of about 1 cm. The current-voltage (I-V) characteristic has been measured over the temperature range 120–380 K. The barrier height is evaluated from the Richardson plot as 0.57 eV, and discussed by taking account of the effects of an interfacial layer between the metal and semiconductor. The capacitance-voltage (C-V) characteristic has been measured at 0.1, 1, and 100 kHz over the temperature range 120–500 K. A frequency dispersion is observed in the C-V characteristic. It is explained by the frequency dispersion in the dielectric constant of the interfacial layer and the capacitive response of trapping states in the interfacial layer and single-crystal parts of polycrystalline GaAs.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.336997

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7

Digitale Medien

Effects of deep Fe acceptors on the impedance of a semi-insulating n-type Fe-doped InP Schottky barrier (1985)

Hattori, K. ; Uraoka, U. ; Fujii, T.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 58 (1985), S. 4626-4632

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The capacitive response of deep Fe acceptors in a semi-insulating n-type Fe-doped InP Schottky barrier has been investigated. The capacitance-voltage (C-V) and conductance-voltage (G-V) characteristics over the frequency range 0.06–100 kHz are measured at 300, 317, and 335 K. Great frequency dispersion is observed in C and G. The reverse bias dependencies of C and (G−G0) are shown to be very weak at high frequencies, where G0 is the dc conductance. As measuring frequency is lowered, (G−G0) decreases but C increases considerably. At low frequencies, the bias dependencies of C and (G−G0) are observed and measured 1/C2 versus reverse bias curves are found to be straight lines. It is shown that at low frequencies, C and (G−G0) take maxima near zero bias and rapidly decrease in a forward bias region. As temperature increases, the frequency region in which such low-frequency characteristics are found extends more widely into a high-frequency range. Theoretical calculations of C and (G−G0) are also carried out. The results are compared with experimental ones. Observed variations of C and G with frequency, bias voltage, and temperature are well explained in terms of the delayed response of deep Fe acceptors.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.336232

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8

Digitale Medien

Be-Cr-doped high-corrosion-resistant magneto-optical disks : 35th annual conference on magnetism and magnetic materials (1991)

Horiai, N. ; Ohashi, T. ; Yoshida, S. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 69 (1991), S. 4764-4766

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The addition of Be to TbFeCo thin-film layers results in the gradual deterioration of carrier-to-noise ratio (CNR) and optimized recording power Pw compared with that of Cr. Be and Cr composite-doped disks, whose CNR maintain over 54 dB at a recording frequency of 1 MHz, prevent bit-error-rate (BER) levels from increasing in accelerated environmental tests. It is noted that even prior to environmental stability testing, BER of Be-Cr composite-doped disks is less than that of nondoped disks. From the results obtained by Auger electron spectroscopy analysis, it is explained that this difference is caused by fluctuations in the reflections of disks resulting from varying thicknesses of extra layers formed as a result of reaction between TbFeCo and SiN. Finally, through the write-erase cycle test and differential scanning calorimetry analysis, it has been demonstrated that Be-Cr-doped disks possess a higher thermal durability than nondoped disks.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.348272

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9

Digitale Medien

Composition dependence of lattice spacing for low dislocation density undoped liquid encapsulated Czochralski GaAs crystals (1991)

Usuda, K. ; Yasuami, S. ; Fujii, T. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 69 (1991), S. 182-184

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Crystals with varied composition were pulled by the As-partial-pressure controlled liquid encapsulated Czochralski method. The dislocation density was found to be as low as 2×103 cm−2 at the cores of the crystals. Lattice spacing (d) was measured with a precision of Δd/d ∼ 5.9 × 10−6 using synchrotron radiation. For a variation of 7×10−5 in the As-atom fraction in the crystals, the lattice spacing varied by less than 1×10−5 A(ring).

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.347740

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10

Digitale Medien

Magnetic anisotropy by ferromagnetic particles alignment in a magnetic field (1990)

Yamaguchi, K. ; Matsumoto, K. ; Fujii, T.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 67 (1990), S. 4493-4495

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Magnetic and optical properties of films composed of ferromagnetic fine particles aligned in a magnetic field were investigated. The spin-coated films were prepared by using a solution of magnetite fine particles dissolved in water-diluted polyvinyl alcohol (PVA) on glass substrates, and followed by drying at 80 °C and solidifying at 200 °C in a magnetic field. Linear-chain clusters of magnetite particles were formed in a considerably weak field below 1 kOe, which give rise to magnetic and optical uniaxial anisotropies. Both properties vary depending on preparation conditions such as the particle concentration, the viscosity of the solution, and the field strength during drying.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.344892

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