12 research outputs found
Nonvolatile ferroelectric control of ferromagnetism in (Ga,Mn)As
There is currently much interest in materials and structures that provide
coupled ferroelectric and ferromagnetic responses, with a long-term goal of
developing new memories and spintronic logic elements. Within the field there
is a focus on composites coupled by magnetostrictive and piezoelectric strain
transmitted across ferromagnetic-ferroelectric interfaces, but substrate
clamping limits the response in the supported multilayer configuration favoured
for devices. This constraint is avoided in a ferroelectric-ferromagnetic
bilayer in which the magnetic response is modulated by the electric field of
the poled ferroelectric. Here, we report the realization of such a device using
a diluted magnetic semiconductor (DMS) channel and a polymer ferroelectric
gate. Polarization reversal of the gate by a single voltage pulse results in a
persistent modulation of the Curie temperature as large as 5%. The device
demonstrates direct and quantitatively understood electric-fieldmediated
coupling in a multiferroic bilayer and may provide new routes to nanostructured
DMS materials and devices via ferroelectric domain nanopatterning. The
successful implementation of a polymer-ferroelectric gate fieldeffect
transistor (FeFET) with a DMS channel adds a new functionality to semiconductor
spintronics and may be of importance for future low-voltage spintronics devices
and memory structures.Comment: 19 pages, 5 figure
Hard scattering in gamma p interactions
We report on the investigation of the final state in interactions of quasi-real photons with protons. The data were taken with the H1 detector at the HERA ep collider. Evidence for hard interactions is seen in both single particle spectra and jet formation. The data can best be described by inclusion of resolved photon processess as predicted by QCD. © 1992.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Proton dissociative rho and elastic phi electroproduction at HERA
The electroproduction of rho mesons with proton diffractive dissociation for
Q^2 > 7 GeV^2 and the elastic electroproduction of Phi mesons for Q^2 > 6 Gev^2
are studied in e^+ p collisions at HERA with the H1 detector, for an integrated
luminosity of 2.8 pb-1. The dependence of the cross sections on P_t^2 and Q^2
is measured, and the vector meson polarisation obtained. The cross section
ratio between proton dissociative and elastic production of rho mesons is
measured and discussed in the framework of the factorisation hypothesis of
diffractive vertices. The ratio of the elastic cross section for Phi and rho
meson production is investigated as a function of Q^2.Comment: 23 pages, 7 Figure
Photoproduction of and at HERA and a Comparison with Deep Inelastic Scattering
Two-particle correlations in invariant mass are studied separately for like-sign and unlike-sign charged particles produced in deep inelastic positron-proton scattering in a new kinematical domain. The data were taken with the H1 detector at the HERA storage ring in 1994, in which 27.5 GeV positrons collided with 820 GeV protons at a centre of mass energy sqrt{s}=300 GeV. The observed enhancement of the like-sign correlations at low invariant masses is related to the dimensions of the hadronic source. The data are compared to different QCD models where the hadronization is performed with the string-fragmentation model. Results are presented for the first time separately for diffractive and non-diffractive scattering, in domains of four-momentum transfer, Bjorken-x, and hadronic center of mass energy, and in intervals of charged particle multiplicity. The observed source radii do not differ strongly from those measured in lower energy lepton-nucleon inelastic scattering, and e^+e^- annihilation
Observation of events at very high Q**2 in e p collisions at HERA
Measurements of ep scattering with squared 4-momentum transfer Q^2 up to
35000 GeV^2 are compared with the expectation of the standard deep-inelastic
model of lepton-nucleon scattering (DIS). For Q^2 > 15000 GeV^2, N_{obs} =12
neutral current candidate events are observed where the expectation is N_DIS =
4.71 \pm 0.76 events. In the same Q^2 range, N_{obs} =4 charged current
candidates are observed where the expectation is N_{DIS} = 1.77 \pm 0.87
events. The probability P(N \geq N_{obs}) that the DIS model signal N
fluctuates to N \geq N_{obs} in a random set of experiments is 6 10^{-3} for
neutral current and 0.14 for charged current. The difference in the observed
and expected number of Neutral Current events is mostly due to events at large
masses M = sqrt{xs} in which the positron is backscattered at large y =
Q^2/M^2.Comment: 30 pages, latex, 8 Figure