162 research outputs found
United States v. Janis: Demise of the Exclusionary Rule and Reinstatement of the Silver Platter Doctrine in Federal Civil Tax Cases
Spin Triplet Supercurrent in Co/Ni Multilayer Josephson Junctions with Perpendicular Anisotropy
We have measured spin-triplet supercurrent in Josephson junctions of the form
S/F'/F/F'/S, where S is superconducting Nb, F' is a thin Ni layer with in-plane
magnetization, and F is a Ni/[Co/Ni]n multilayer with out-of-plane
magnetization. The supercurrent in these junctions decays very slowly with
F-layer thickness, and is much larger than in similar junctions not containing
the two F' layers. Those two features are the characteristic signatures of
spin-triplet supercurrent, which is maximized by the orthogonality of the
magnetizations in the F and F' layers. Magnetic measurements confirm the
out-of-plane anisotropy of the Co/Ni multilayers. These samples have their
critical current optimized in the as-prepared state, which will be useful for
future applications.Comment: 4 pages, 4 figures, formatted in RevTeX version 4. Submitted to
Physical Review B on August 13th, 201
Limits of magnetic interactions in Ni-Nb ferromagnet-superconductor bilayers
Studies of ferromagnet-superconductor hybrid systems have uncovered magnetic
interactions between the competing electronic orderings. The Electromagnetic
Proximity Effect predicts the formation of a spontaneous vector potential
inside a superconductor placed in proximity to a ferromagnet. In this work, we
use a Nb superconducting layer and Ni ferromagnetic layer to test for such
magnetic interactions. We use the complementary, but independent, techniques of
polarised neutron reflectometry and detection Josephson junctions to probe the
magnetic response inside the superconducting layer at close to zero applied
field. In this condition, Meissner screening is negligible, so our measurements
examine only additional magnetic and screening contributions from proximity
effects. We report that any signals attributable to such proximity effects are
below the detection resolution of our experimental study. We estimate a limit
of the size of the zero field Electromagnetic Proximity Effect in our Ni-Nb
samples to be 0.27 mT from our measurements.Comment: Main text 18 pages, 4 figures, 1 table. Plus SI 8 pages, 6 figure
Distortions to the penetration depth and coherence length of superconductor/normal-metal superlattices
Superconducting (S) thin film superlattices composed of Nb and a normal-metal spacer (N) have been extensively utilized in Josephson junctions given their favorable surface roughness compared to Nb films of comparable thickness. In this work, we characterize the London penetration depth and Ginzburg-Landau coherence lengths of S/N superlattices using polarized neutron reflectometry and electrical transport. Despite the normal-metal spacer layers being only approximately 8% of the total superlattice thickness, we surprisingly find that the introduction of these thin N spacers between S layers leads to a dramatic increase in the measured London penetration depth compared to that of a single Nb film of comparable thickness. Using the measured values for the effective in- and out-of-plane coherence lengths, we quantify the induced anisotropy of the superlattice samples and compare to a single Nb film sample. From these results, we find that the superlattices behave similarly to layered 2D superconductors
Making Operation-based CRDTs Operation-based
Conflict-free Replicated Datatypes can simplify the design of predictable eventual consistency. They can be classified into state-based or operation-based. Operation-based approaches have the potential for allowing compact designs in both the sent message and the object state size, but cur- rent approaches are still far from this objective. Here we explore the design space for operation-based solutions, and we leverage the interaction with the middleware by offering a technique that delivers very compact solutions, while only broadcasting operation names and arguments.(undefined)(undefined
Nitrogen-Based Magneto-Ionic Manipulation of Exchange Bias in CoFe/MnN Heterostructures
Electric field control of the exchange bias effect across
ferromagnet/antiferromagnet (FM/AF) interfaces has offered exciting potentials
for low-energy-dissipation spintronics. In particular, the solid state
magneto-ionic means is highly appealing as it may allow reconfigurable
electronics by transforming the all-important FM/AF interfaces through ionic
migration. In this work, we demonstrate an approach that combines the
chemically induced magneto-ionic effect with the electric field driving of
nitrogen in the Ta/CoFe/MnN/Ta structure to electrically
manipulate exchange bias. Upon field-cooling the heterostructure, ionic
diffusion of nitrogen from MnN into the Ta layers occurs. A significant
exchange bias of 618 Oe at 300 K and 1484 Oe at 10 K is observed, which can be
further enhanced after a voltage conditioning by 5% and 19%, respectively. This
enhancement can be reversed by voltage conditioning with an opposite polarity.
Nitrogen migration within the MnN layer and into the Ta capping layer cause the
enhancement in exchange bias, which is observed in polarized neutron
reflectometry studies. These results demonstrate an effective nitrogen-ion
based magneto-ionic manipulation of exchange bias in solid-state devices.Comment: 28 pages, 4 figures; supporting information: 17 pages, 11 figure
Probing elastic and inelastic breakup contributions to intermediate-energy two-proton removal reactions
The two-proton removal reaction from 28Mg projectiles has been studied at 93
MeV/u at the NSCL. First coincidence measurements of the heavy 26Ne projectile
residues, the removed protons and other light charged particles enabled the
relative cross sections from each of the three possible elastic and inelastic
proton removal mechanisms to be determined. These more final-state-exclusive
measurements are key for further interrogation of these reaction mechanisms and
use of the reaction channel for quantitative spectroscopy of very neutron-rich
nuclei. The relative and absolute yields of the three contributing mechanisms
are compared to reaction model expectations - based on the use of eikonal
dynamics and sd-shell-model structure amplitudes.Comment: Accepted for publication in Physical Review C (Rapid Communication
Elastic breakup cross sections of well-bound nucleons
The 9Be(28Mg,27Na) one-proton removal reaction with a large proton separation
energy of Sp(28Mg)=16.79 MeV is studied at intermediate beam energy.
Coincidences of the bound 27Na residues with protons and other light charged
particles are measured. These data are analyzed to determine the percentage
contributions to the proton removal cross section from the elastic and
inelastic nucleon removal mechanisms. These deduced contributions are compared
with the eikonal reaction model predictions and with the previously measured
data for reactions involving the re- moval of more weakly-bound protons from
lighter nuclei. The role of transitions of the proton between different bound
single-particle configurations upon the elastic breakup cross section is also
quantified in this well-bound case. The measured and calculated elastic breakup
fractions are found to be in good agreement.Comment: Phys. Rev. C 2014 (accepted
First-order phase transition vs. spin-state quantum-critical scenarios in strain-tuned epitaxial cobaltite thin films
Pr-containing perovskite cobaltites exhibit unusual valence transitions,
coupled to coincident structural, spin-state, and metal-insulator transitions.
Heteroepitaxial strain was recently used to control these phenomena in the
model (PrY)CaCoO system, stabilizing a
nonmagnetic insulating phase under compression (with a room-temperature
valence/spin-state/metal-insulator transition) and a ferromagnetic metallic
phase under tension, thus exposing a potential spin-state quantum critical
point. The latter has been proposed in cobaltites and can be probed in this
system as a function of a disorder-free variable (strain). We study this here
via thickness-dependent strain relaxation in compressive
SrLaAlO(001)/(PrY)CaCoO
epitaxial thin films to quasi-continuously probe structural, electronic, and
magnetic behaviors across the nonmagnetic-insulator/ferromagnetic-metal
boundary. High-resolution X-ray diffraction, electronic transport,
magnetometry, polarized neutron reflectometry, and temperature-dependent
magnetic force microscopy provide a detailed picture, including abundant
evidence of temperature- and strain-dependent phase coexistence. This indicates
a first-order phase transition as opposed to spin-state quantum-critical
behavior, which we discuss theoretically via a phenomenological Landau model
for coupled spin-state and magnetic phase transitions.Comment: main text + supplementary materia
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