1,363 research outputs found
Current-perpendicular-to-plane giant magnetoresistance of a spin valve using Co2MnSi Heusler alloy electrodes
We report the current-perpendicular-to-plane giant magnetoresistance of a
spin valve with Co2MnSi (CMS) Heusler alloy ferromagnetic electrodes. A
multilayer stack of Cr/Ag/Cr/CMS/Cu/CMS/Fe25Co75/Ir28Mn72/Ru was deposited on a
MgO (001) single crystal substrate. The bottom CMS layer was epitaxially grown
on the Cr/Ag/Cr buffer layers and was ordered to the L21 structure after
annealing at 673 K. The upper CMS layer was found to grow epitaxially on the Cu
spacer layer despite the large lattice mismatch between Cu and CMS. The highest
MR ratios of 8.6% and 30.7% for CPP-GMR were recorded at room temperature and 6
K, respectively. The high spin polarization of the epitaxial CMS layers is the
most likely origin of the high MR ratio.Comment: 14 pages, 3 figures, presented at the 53rd Annual Conference on
Magnetism and Magnetic Materials, to be published in J. Appl. Phy
Quasi-classical path integral approach to supersymmetric quantum mechanics
{}From Feynman's path integral, we derive quasi-classical quantization rules
in supersymmetric quantum mechanics (SUSY-QM). First, we derive a SUSY
counterpart of Gutzwiller's formula, from which we obtain the quantization rule
of Comtet, Bandrauk and Campbell when SUSY is good. When SUSY is broken, we
arrive at a new quantization formula, which is found as good as and even
sometime better than the WKB formula in evaluating energy spectra for certain
one-dimensional bound state problems. The wave functions in the stationary
phase approximation are also derived for SUSY and broken SUSY cases. Insofar as
a broken SUSY case is concerned, there are strong indications that the new
quasi-classical approximation formula always overestimates the energy
eigenvalues while WKB always underestimates.Comment: 13 pages + 5 figures, complete paper submitted as postscript file, to
appear in Phys. Rev.
Hall effect in laser ablated Co_2(Mn,Fe)Si thin films
Pulsed laser deposition was employed to grow thin films of the Heusler
compounds Co_2MnSi and Co_2FeSi. Epitaxial growth was realized both directly on
MgO (100) and on a Cr or Fe buffer layer. Structural analysis by x-ray and
electron diffraction shows for both materials the ordered L2_1 structure. Bulk
magnetization was determined with a SQUID magnetometer. The values agree with
the Slater-Pauling rule for half-metallic Heusler compounds. On the films grown
directly on the substrate measurements of the Hall effect have been performed.
The normal Hall effect is nearly temperature independent and points towards a
compensated Fermi surface. The anomalous contribution is found to be dominated
by skew scattering. A remarkable sign change of both normal and anomalous Hall
coefficients is observed on changing the valence electron count from 29 (Mn) to
30 (Fe).Comment: 9 pages, 6 figures submitted to J Phys
Equation of Motion for a Spin Vortex and Geometric Force
The Hamiltonian equation of motion is studied for a vortex occuring in
2-dimensional Heisenberg ferromagnet of anisotropic type by starting with the
effective action for the spin field formulated by the Bloch (or spin) coherent
state. The resultant equation shows the existence of a geometric force that is
analogous to the so-called Magnus force in superfluid. This specific force
plays a significant role for a quantum dynamics for a single vortex, e.g, the
determination of the bound state of the vortex trapped by a pinning force
arising from the interaction of the vortex with an impurity.Comment: 13 pages, plain te
Path integral for a relativistic Aharonov-Bohm-Coulomb system
The path integral for the relativistic spinless Aharonov-Bohm-Coulomb system
is solved, and the energy spectra are extracted from the resulting amplitude.Comment: 6 pages, Revte
Possible observation of energy level quantization in an intrinsic Josephson junction
Energy level quantization (ELQ) is studied to clarify the macroscopic quantum
dynamics of the d-wave Josephson junction (JJ). The influences of the nodal
quasiparticles of d-wave superconductivity on the damping effect are
numerically evaluated on the basis of a phenomenological model. The
calculation, based on realistic parameters for a Bi2Sr2CaCu2O8+d (Bi2212)
intrinsic JJ, shows that the observation of ELQ is possible when the sweep rate
of the bias current exceeds 10 A/sec. High-sweep- rate measurements (121A/sec)
performed on a Bi2212 intrinsic JJ result in the appearance of multiple peaks
in the switching current distribution suggesting the realization of ELQ in the
d-wave JJ.Comment: 5 pages, 3 figure
Frequency banded wave characteristic observed by GPS buoys off the Pacific coast of Japan
Fifteen GPS buoys, which measure the vertical motion of the buoy due to waves and tides by the RTKGPS technology, are moored at a spot of 100-400 m in water depth and within 10-20 km from the shoreline around the Japanese coast. They are the newest equipment on the Nationwide Ocean Wave Information Network for Port and Harbours (NOWPHAS). This study conducted the statistical analysis on four frequency banded wave components (short-period wind wave, long-period wind wave, swell and infra-gravity wave) acquired by the GPS buoys and their nearby coastal wave gauges. A high correlation was found in these frequency banded wave heights, in particular two long period components between a GPS buoy and its nearby coastal wave gauge. The correlation between the long period wave component heights and the significant wave height at the GPS buoys is high, while the ratio of the swell height to the significant wave height varies with the incident wave direction and the meteorological conditions. The\ud
swell direction sometimes differs from the wind wave direction. The ratio of the swell height to the significant wave height in the entire band varies around the time when the significant wave height reached its maximum during the 2009 Typhoon Melor event
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