Journal of Applied Physics
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The effect of a trailing shield for perpendicular write heads
Journal of Applied Physics - Tập 99 Số 8 - 2006
Porous silicon formation mechanisms Recent reports describing photoluminescence in porous silicon have heightened the level of interest in it as a unique electronic material, and have created a need for a more complete understanding of the mechanism of porous silicon formation. The various models describing porous silicon formation are reviewed and the known electrochemical and morphological properties are discussed with the intention of unifying the different models into a comprehensive explanation for the formation of a porous structure in silicon. Because the specific surface dissolution chemistry is critical for a complete understanding of pore formation, some of the more prominent dissolution reactions are also reviewed and their relative importance to pore generation and morphology is discussed. Some aspects of the recently reported quantum effects are also reviewed. Because the mechanism of porous silicon formation involves a wide range of interdisciplinary fields, a considerable number of analogies and examples to related phenomena are also presented throughout the review to aid comprehension.
Journal of Applied Physics - Tập 71 Số 8 - Trang R1-R22 - 1992
Critical exponents of the La0.7Sr0.3MnO3, La0.7Ca0.3MnO3, and Pr0.7Ca0.3MnO3 systems showing correlation between transport and magnetic properties From the low-temperature (down to 10K) dc-magnetization data of the La0.7Sr0.3MnO3 (LSM), La0.7Ca0.3MnO3 (LCM), and Pr0.7Ca0.3MnO3 (PCM) systems, we estimated the critical exponents β, γ, and hence δ from the analysis of the modified Arrot plots. The exponent β estimated for the LCM system is less than that predicted by Heisenberg model and resides within the zone predicted by Ising model while for the LSM sample, β is higher than that predicted from the Heisenberg model which is considered to be due to the presence of dipole-dipole interaction arising from the large spin moment in the LSM system. The magnetization data of the PCM system cannot be fitted to the modified Arrot plots, which suggest highly inhomogeneous ground state even under 5T magnetic field. Both LSM and LCM have almost equal values of γ. Seebeck coefficient data indicate a crossover from higher-temperature n-type to lower-temperature p-type conductivity behavior in both LSM and LCM systems, while the semiconducting PCM system shows p-type conductivity throughout the temperature range (300–80K). It is noticed that for LSM system TC (Curie temperature) and TMI (metal-insulator transition temperature) are almost equal (∼360K), whereas for the LCM system there exist a large difference between TC and TMI (TC∼245K and TMI∼265K), which may give some idea regarding the critical behavior of the respective samples.
Journal of Applied Physics - Tập 98 Số 10 - 2005
Localized stimulation of neural tissues in the brain by means of a paired configuration of time-varying magnetic fields A method of localized stimulation of the human brain is proposed. The basic idea is to concentrate induced eddy currents locally in the vicinity of a target in the cortex by a pair of coils which are positioned outside the head so that time-varying magnetic fields pass through the head in the opposite directions around a target. The eddy currents induced at the target are expected to flow together, which results in an increased current flow at the target. Spatial distributions of induced eddy currents are calculated in cubical and spherical volume conductor models by a finite element method. The results show that the current vectors make themselves two vortexes which flow together at the target. The current density at the target makes a peak which is higher by 2–3 times than current densities at nontarget regions. The validity of the proposed method is demonstrated by experiments using frog nerve-muscle preparations.
Journal of Applied Physics - Tập 64 Số 10 - Trang 5862-5864 - 1988
Structural effects on Stokes and anti-Stokes luminescence of double-perovskite (Ba,Sr)2CaMoO6: Yb3+,Eu3+ This paper deals with the investigation of structural effects on Stokes and anti-Stokes luminescence properties of double-perovskite (Ba,Sr)2CaMoO6: Eu3+,Yb3+. It is found that the tilting of the (Ca/Mo)O6 octahedra framework favors energy transfer from the MoO6 group to Eu3+/Yb3+ at the B site for Stokes luminescence processes, in which the structural connectivity angle ∠Mo–O–Eu/Yb is slightly smaller than 180°. While Eu3+/Yb3+ at the A site with a structural connectivity angle ∠Mo–O–Eu/Yb of around 90° least benefits the energy transfer. The linear connectivity of Yb–O–Mo–O–Eu with or without tilting of the (Ca/Mo)O6 framework for Eu3+ and Yb3+ at the B site strongly restrains the anti-Stokes luminescence. Whereas, it shows normal anti-Stokes luminescence for Eu3+ or Yb3+ at the A site and Yb3+ or Eu3+ at the B site with ∠Yb–O–Eu of around 90°. This research may open up promising new perspectives for designing novel luminescent materials with high efficiency.
Journal of Applied Physics - Tập 110 Số 1 - 2011
Measurement of Third-Order Moduli of Silicon and Germanium Experimental techniques for determining third-order moduli of single crystals by means of ultrasonic wave propagation are described. Results for silicon and germanium demonstrate a good degree of self-consistency among the basic experimental data obtained with both hydrostatic and uniaxial pressure.
In units of 1012 dyn/cm2 and for 25°C, the third-order moduli are: ModulusValue for SiValue for GeC111−8.25±0.10−7.10±0.06C112−4.51±0.05−3.89±0.03C123−0.64±0.10−0.18±0.06C144+0.12±0.25−0.23±0.16C166−3.10±0.10−2.92±0.08C456−0.64±0.20−0.53±0.07Thermodynamic definitions for the moduli (K. Brugger, Phys. Rev. 133, A1611 (1964)] have been used.
Journal of Applied Physics - Tập 35 Số 11 - Trang 3312-3319 - 1964
Preparation and properties of sputter-deposited crystalline ultrafine particles The composition and size dependence of the magnetic properties of crystalline Fe-Co and Ni ultrafine particles has been investigated. Samples were prepared by sputter deposition onto sputter-etched polyimide substrates. Little difference between the magnetic properties of crystalline and amorphous particles was found in Fe-rich alloys, but we found a greater influence of magnetocrystalline anisotropy in Co-rich alloys. When the particles are larger than 2500 Å, the samples have negative anisotropy Ku (easy direction parallel to the substrate plane). As the particle diameter decreases, Ku becomes positive, and the coercive field Hc increases from a few hundred oersteds to a maximum of more than 1000 Oe. Below a particle diameter of about 1000 Å, Ms , Ku, and Hc all drop rapidly toward zero, presumably due to the appearance of superparamagnetism. Annealing above about 200 °C leads to significant increases in Hc, Ku, and Ms, and also to significant changes in the line shapes of the x-ray diffraction patterns, as a result of stress relaxation. A low-temperature diffusion process leading to changes in the morphology of the subparticles may also be a cause of the increment of magnetic properties on annealing.
Journal of Applied Physics - Tập 63 Số 8 - Trang 4243-4245 - 1988
Ultrafine particles of Fe, Co, and Ni ferromagnetic metals Fe, Co, and Ni ultrafine particles (UFP) were prepared by a gas evaporation method in an inert atmosphere. The different preparing conditions of the Fe, Co, and Ni UFP included inert gas pressures and kinds were investigated by means of x-ray diffraction, transmission electron microscopy (TEM), and magnetic measurements with low or high temperatures. The experimental results show that coercivities Hc of the Fe, Co, and Ni UFP, depending on particle sizes, obey a single-domain theory. The maximum Hc was 450, 1000, and 1500 Oe, respectively, for Ni (310 Å), Fe (210 Å), and Co (200 Å) at room temperature. The coercivities came up to high in the low temperatures. The saturation magnetizations Ms of the Fe, Co, and Ni UFP decreased with small particle sizes. A face-centered structure of Co UFP (200–300 Å) was confirmed by x-ray diffraction. Some Fe UFP in the shape of balls (200–400 Å) observed in the TEM may be an amorphous structure.
Journal of Applied Physics - Tập 69 Số 8 - Trang 5119-5121 - 1991
Nucleation and growth kinetics during metal-induced layer exchange crystallization of Ge thin films at low temperatures The kinetics of Al-catalyzed layer exchange crystallization of amorphous germanium (Ge) thin films at low temperatures is reported. Observation of Ge mass transport from an underlying amorphous Ge layer to the Al film surface through an interposed sub-nanometer GeOx interfacial layer allows independent measurement of the areal density and average area of crystalline Ge islands formed on the film surface. We show that bias-voltage stressing of the interfacial layer can be used to control the areal density of nucleated Ge islands. Based on experimental observations, the Johnson-Mehl-Avrami-Kolmogorov phase transformation theory is used to model nanoscale nucleation and growth of Ge islands in two dimensions. Ge island nucleation kinetics follows an exponentially decaying nucleation rate with time. Ge island growth kinetics switches from linear growth at a constant growth velocity to diffusion-limited growth as the growth front advances. The transition point between these two regimes depends on the Ge nucleation site density and the annealing temperature. Knowledge of the kinetics of low-temperature crystallization is important in achieving textured polycrystalline Ge thin films with large grains for applications in large-area electronics and solar energy conversion.
Journal of Applied Physics - Tập 111 Số 4 - 2012
Identification of the symmetry of phonon modes in CsPbCl3 in phase IV by Raman and resonance-Raman scattering The first- and second-order Raman phonon spectra of CsPbCl3 were measured in phase IV using Raman and resonance-Raman scattering. Twelve Raman active phonons were resolved at 32, 35.5, 42, 52, 72, 90, 110, 115, 121, 189, 200.5, and 375 cm−1 and correlated to the phonon spectrum of CsPbCl3 in phase I. The highest frequency longitudinal optical mode is 375 cm−1.
Journal of Applied Physics - Tập 82 Số 11 - Trang 5391-5395 - 1997
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