1,182 research outputs found
Anisotropic magnetoresistance in a 2DEG in a quasi-random magnetic field
We present magnetotransport results for a 2D electron gas (2DEG) subject to
the quasi-random magnetic field produced by randomly positioned sub-micron Co
dots deposited onto the surface of a GaAs/AlGaAs heterostructure. We observe
strong local and non-local anisotropic magnetoresistance for external magnetic
fields in the plane of the 2DEG. Monte-Carlo calculations confirm that this is
due to the changing topology of the quasi-random magnetic field in which
electrons are guided predominantly along contours of zero magnetic field.Comment: 4 pages, 6 figures, submitted to Phys. Rev.
Linear magnetoresistance in commercial n-type silicon due to inhomogeneous doping
Free electron theory tells us that resistivity is independent of magnetic
field. In fact, most observations match the semiclassical prediction of a
magnetoresistance that is quadratic at low fields before saturating. However, a
non-saturating linear magnetoresistance has been observed in exotic
semiconductors such as silver chalcogenides, lightly-doped InSb, N-doped InAs,
MnAs-GaAs composites, PrFeAsO, and epitaxial graphene. Here we report the
observation of a large linear magnetoresistance in the ohmic regime in
commonplace commercial n-type silicon wafer. It is well-described by a
classical model of spatially fluctuating donor densities, and may be amplified
by altering the aspect ratio of the sample to enhance current-jetting:
increasing the width tenfold increased the magnetoresistance at 8 T from 445 %
to 4707 % at 35 K. This physical picture may well offer insights into the large
magnetoresistances recently observed in n-type and p-type Si in the non-ohmic
regime.Comment: submitted to Nature Material
Parameter estimation supplement to the Mission Analysis Evaluation and Space Trajectory Operations program (MAESTRO)
This Parameter Estimation Supplement describes the PEST computer program and gives instructions for its use in determination of lunar gravitation field coefficients. PEST was developed for use in the RAE-B lunar orbiting mission as a means of lunar field recovery. The observations processed by PEST are short-arc osculating orbital elements. These observations are the end product of an orbit determination process obtained with another program. PEST's end product it a set of harmonic coefficients to be used in long-term prediction of the lunar orbit. PEST employs some novel techniques in its estimation process, notably a square batch estimator and linear variational equations in the orbital elements (both osculating and mean) for measurement sensitivities. The program's capabilities are described, and operating instructions and input/output examples are given. PEST utilizes MAESTRO routines for its trajectory propagation. PEST's program structure and subroutines which are not common to MAESTRO are described. Some of the theoretical background information for the estimation process, and a derivation of linear variational equations for the Method 7 elements are included
Towards experimental entanglement connection with atomic ensembles in the single excitation regime
We present a protocol for performing entanglement connection between pairs of
atomic ensembles in the single excitation regime. Two pairs are prepared in an
asynchronous fashion and then connected via a Bell measurement. The resulting
state of the two remaining ensembles is mapped to photonic modes and a reduced
density matrix is then reconstructed. Our observations confirm for the first
time the creation of coherence between atomic systems that never interacted, a
first step towards entanglement connection, a critical requirement for quantum
networking and long distance quantum communications
Mechanism of temperature dependence of the magnetic anisotropy energy in ultrathin Cobalt and Nickel films
Temperature dependent FMR-measurements of Ni and Co films are analysed using
a microscopic theory for ultrathin metallic systems. The mechanism governing
the temperature dependence of the magnetic anisotropy energy is identified and
discussed. It is reduced with increasing temperature. This behavior is found to
be solely caused by magnon excitations.Comment: 3 pages, 4 figures III Joint European Magnetic Symposia, San
Sebastian, Spai
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