9 research outputs found
Piezoelectric nanoelectromechanical resonators based on aluminum nitride thin films
We demonstrate piezoelectrically actuated, electrically tunable nanomechanical resonators based on multilayers containing a 100-nm-thin aluminum nitride (AlN) layer. Efficient piezoelectric actuation of very high frequency fundamental flexural modes up to ~80 MHz is demonstrated at room temperature. Thermomechanical fluctuations of AlN cantilevers measured by optical interferometry enable calibration of the transduction responsivity and displacement sensitivities of the resonators. Measurements and analyses show that the 100 nm AlN layer employed has an excellent piezoelectric coefficient, d_(31)=2.4 pm/V. Doubly clamped AlN beams exhibit significant frequency tuning behavior with applied dc voltage
Giant and reversible extrinsic magnetocaloric effects in La0.7Ca0.3MnO3 films due to strain
Large thermal changes driven by a magnetic field have been proposed for
environmentally friendly energy efficient refrigeration, but only a few
materials which suffer hysteresis show these giant magnetocaloric effects. Here
we create giant and reversible extrinsic magnetocaloric effects in epitaxial
films of the ferromagnetic manganite La0.7Ca0.3MnO3 using strain mediated
feedback from BaTiO3 substrates near a first-order structural phase transition.
Our findings should inspire the discovery of giant magnetocaloric effects in a
wide range of magnetic materials, and the parallel development of
nanostructured bulk samples for practical applications.Comment: 32 pages, 1 Table, 5 figures, supplementary informatio
Measurement of the Beam-Recoil Polarization in Low-Energy Virtual Compton Scattering from the Proton
Double-polarization observables in the reaction have been measured at . The experiment
was performed at the spectrometer setup of the A1 Collaboration using the 855
MeV polarized electron beam provided by the Mainz Microtron (MAMI) and a recoil
proton polarimeter. From the double-polarization observables the structure
function is extracted for the first time, with the value , using the low-energy theorem
for Virtual Compton Sattering. This structure function provides a hitherto
unmeasured linear combination of the generalized polarizabilities of the
proton
A new measurement of the structure functions and in virtual Compton scattering at 0.33 (GeV/c)
The cross section of the reaction has been measured at
(GeV/c). The experiment was performed using the electron beam
of the MAMI accelerator and the standard detector setup of the A1
Collaboration. The cross section is analyzed using the low-energy theorem for
virtual Compton scattering, yielding a new determination of the two structure
functions P_LL}-P_{TT}/epsilon and which are linear combinations of
the generalized polarizabilities of the proton. We find somewhat larger values
than in the previous investigation at the same . This difference, however,
is purely due to our more refined analysis of the data. The results tend to
confirm the non-trivial -evolution of the generalized polarizabilities and
call for more measurements in the low- region ( 1 (GeV/c)).Comment: 9 pages, 10 figures. EPJA version. slight revisions in the text and
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Beam-helicity asymmetry in photon and pion electroproduction in the Delta(1232) resonance region at Q^2= 0.35 (GeV/c)^2
The beam-helicity asymmetry has been measured simultaneously for the
reactions (e p \to e p \gamma) and (e p \to e p \pi^0) in the
resonance region at 0.35 (GeV/c). The experiment was performed at
MAMI with a longitudinally polarized beam and an out-of-plane detection of the
proton. The results are compared with calculations based on Dispersion
Relations for virtual Compton scattering and with the MAID model for pion
electroproduction. There is an overall good agreement between experiment and
theoretical calculations. The remaining discrepancies may be ascribed to an
imperfect parametrization of some multipoles, mainly
contributing to the non-resonant background. The beam-helicity asymmetry in
both channels ( and ) shows a good sensitivity to these
multipoles and should allow future improvement in their parametrization.Comment: 7 pages, 8 figures, version to appear in EPJ