115 research outputs found
Uncompensated magnetization and exchange-bias field in LaSrMnO/YMnO bilayers: The influence of the ferromagnetic layer
We studied the magnetic behavior of bilayers of multiferroic and nominally
antiferromagnetic o-YMnO (375~nm thick) and ferromagnetic
LaSrMnO and LaCaMnO (nm), in particular the vertical magnetization shift and exchange
bias field for different thickness and magnetic dilution of the
ferromagnetic layer at different temperatures and cooling fields. We have found
very large shifts equivalent to up to 100\% of the saturation value of
the o-YMO layer alone. The overall behavior indicates that the properties of
the ferromagnetic layer contribute substantially to the shift and that
this does not correlate straightforwardly with the measured exchange bias field
.Comment: 10 figures, 8 page
On the low-field Hall coefficient of graphite
We have measured the temperature and magnetic field dependence of the Hall
coefficient () in three, several micrometer long multigraphene
samples of thickness between to ~nm in the temperature range
0.1 to 200~K and up to 0.2~T field. The temperature dependence of the
longitudinal resistance of two of the samples indicates the contribution from
embedded interfaces running parallel to the graphene layers. At low enough
temperatures and fields is positive in all samples, showing a
crossover to negative values at high enough fields and/or temperatures in
samples with interfaces contribution. The overall results are compatible with
the reported superconducting behavior of embedded interfaces in the graphite
structure and indicate that the negative low magnetic field Hall coefficient is
not intrinsic of the ideal graphite structure.Comment: 10 pages with 7 figures, to be published in AIP Advances (2014
Josephson-coupled superconducting regions embedded at the interfaces of highly oriented pyrolytic graphite
Transport properties of a few hundreds of nanometers thick (in
the graphene plane direction) lamellae of highly oriented pyrolytic graphite
(HOPG) have been investigated. Current–voltage characteristics as well as
the temperature dependence of the voltage at different fixed input currents
provide evidence for Josephson-coupled superconducting regions embedded in
the internal two-dimensional interfaces of HOPG, reaching zero resistance at low
enough temperatures
Evidence for semiconducting behavior with a narrow band gap of Bernal graphite
We have studied the resistivity of a large number of highly oriented graphite
samples with areas ranging from several mm to a few m and
thickness from nm to several tens of micrometers. The measured
resistance can be explained by the parallel contribution of semiconducting
graphene layers with low carrier density cm and the one from
metallic-like internal interfaces. The results indicate that ideal graphite
with Bernal stacking structure is a narrow-gap semiconductor with an energy gap
meV.Comment: 14 pages, 4 Figures, to be published in New Journal of Physics (in
press, 2012
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