1,560 research outputs found
Spin dynamics in a superconductor / ferromagnet proximity system
The ferromagnetic resonance of thin sputtered Ni80Fe20 films grown on Nb is
measured. By varying the temperature and thickness of the Nb the role of the
superconductivity on the whole ferromagnetic layer in these heterostructures is
explored. The change in the spin transport properties below the superconducting
transition of the Nb is found to manifest itself in the Ni80Fe20 layer by a
sharpening in the resonance of the ferromagnet, or a decrease in the effective
Gilbert damping co-efficient. This dynamic proximity effect is in contrast to
low frequency studies in these systems, where the effect of the superconductor
is confined to a small region in the ferromagnet. We interpret this in terms of
the spin pumping model.Comment: 4 pages, 4 figures, to be submitted for publicatio
Sudden Critical Current Drops Induced in S/F Structures
In the search for new physical properties of S/F structures, we have found
that the superconductor critical current can be controlled by the domain state
of the neighboring ferromagnet. The superconductor is a thin wire of thickness
d_{s} ~ 2 xi_{S}. Nb/Co and Nb/Py (Permalloy Ni_{80}Fe_{20}) bilayer structures
were grown with a significant magnetic anisotropy. Critical current
measurements of Nb/Co structures with ferromagnet thickness d_{F} > 30nm show
sudden drops in two very defined steps when the measurements are made along the
hard axes direction (i.e. current track parallel to hard anisotropy axes
direction). These drops disappear when they are made along the easy axis
direction or when the ferromagnet thickness is below 30nm. The drops are
accompanied by vortex flux flow. In addition magnetorestistance measurements
close to Tc show a sharp increase near saturation fields of the ferromagnet.
Similar results are reproduced in Nb/Py bilayer structure with the ferromagnet
thickness d_{F} ~ 50nm along the easy anisotropy axes. These results are
explained as being due to spontaneous vortex formation and flow induced by
Bloch domain walls of the ferromagnet underneath. We argue these Bloch domain
walls produce a 2D vortex-antivortex lattice structure.Comment: 6 pages, 6 figure
Fermi surface and superconductivity in low-density high-mobility {\delta}-doped SrTiO3
The electronic structure of low-density n-type SrTiO3 delta-doped
heterostructures is investigated by angular dependent Shubnikov-de Haas
oscillations. In addition to a controllable crossover from a three- to
two-dimensional Fermi surface, clear beating patterns for decreasing dopant
layer thicknesses are found. These indicate the lifting of the degeneracy of
the conduction band due to subband quantization in the two-dimensional limit.
Analysis of the temperature-dependent oscillations shows that similar effective
masses are found for all components, associated with the splitting of the light
electron pocket. The dimensionality crossover in the superconducting state is
found to be distinct from the normal state, resulting in a rich phase diagram
as a function of dopant layer thickness.Comment: 4 pages, 5 figures, submitted for publicatio
Untrustworthy People Grab Our Attention - Whether We Want Them to or Not
Our automatic attention to injustices and untrustworthy people has the potential to distract us from more relevant concerns. It can make us overly cautious and wary of risk-taking. It can even cause errors in decision-making. There could be a negative impact on our surroundings when we focus on untrustworthy people as a result of second- or third-hand information.York’s Knowledge Mobilization Unit provides services and funding for faculty, graduate students, and community organizations seeking to maximize the impact of academic research and expertise on public policy, social programming, and professional practice. It is supported by SSHRC and CIHR grants, and by the Office of the Vice-President Research & Innovation.
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www.researchimpact.c
Retribution Drives Our Decisions to Punish, but Punishment Is Not the Only Moral Choice
When people decide to punish others, their choice is driven almost entirely by retribution. However, the decision not to punish, although often interpreted as self-interested or morally disinterested, may in fact be based on powerful moral self-reflection and considerations.York's Knowledge Mobilization Unit provides services and funding for faculty, graduate students, and community organizations seeking to maximize the impact of academic research and expertise on public policy, social programming, and professional practice. It is supported by SSHRC and CIHR grants, and by the Office of the Vice-President Research & Innovation.
[email protected]
www.researchimpact.c
Dominant mobility modulation by the electric field effect at the LaAlO_3 / SrTiO_3 interface
Caviglia et al. [Nature (London) 456, 624 (2008)] have found that the
superconducting LaAlO_3 / SrTiO_3 interface can be gate modulated. A central
issue is to determine the principal effect of the applied electric field. Using
magnetotransport studies of a gated structure, we find that the mobility
variation is almost five times as large as the sheet carrier density.
Furthermore, superconductivity can be suppressed at both positive and negative
gate bias. These results indicate that the relative disorder strength strongly
increases across the superconductor-insulator transition.Comment: 4 pages, 4 figure
People Who Punish or Reward Tend to Moralize Even Conventional Behaviour
Managers who have to reward or punish
others may be prone to moralizing. This
can create problems because it may
make the manager less tolerant of
errant behavior while others in the social
group, who may be wary of moralizing
attitudes, may react against the
manager.York's Knowledge Mobilization Unit provides services and funding for faculty, graduate students, and community organizations seeking to maximize the impact of academic research and expertise on public policy, social programming, and professional practice. It is supported by SSHRC and CIHR grants, and by the Office of the Vice-President Research & Innovation.
[email protected]
www.researchimpact.c
Intrinsic spin-orbit coupling in superconducting {\delta}-doped SrTiO3 heterostructures
We report the violation of the Pauli limit due to intrinsic spin-orbit
coupling in SrTiO3 heterostructures. Via selective doping down to a few
nanometers, a two-dimensional superconductor is formed, geometrically
suppressing orbital pair-breaking. The spin-orbit scattering is exposed by the
robust in-plane superconducting upper critical field, exceeding the Pauli limit
by a factor of 4. Transport scattering times several orders of magnitude higher
than for conventional thin film superconductors enables a new regime to be
entered, where spin-orbit coupling effects arise non-perturbatively.Comment: main text 4 pages with 4 figures, supplemental material 2 pages with
2 figure, submitted for publicatio
Magnetotransport effects in polar versus non-polar SrTiO3 based heterostructures
Anisotropic magnetoresistance and negative magnetoresistance for in-plane
fields are compared for the LaAlO3 /SrTiO3 interface and the symmetric Nb-doped
SrTiO3 heterostructure. Both effects are exceptionally strong in LaAlO3 /SrTiO3
. We analyze their temperature, magnetic field and gate voltage dependencies
and find them to arise from a Rashba type spin-orbit coupling with magnetic
scatterers that have two contributions to their potential: spin exchange and
Coulomb interaction. Atomic spin-orbit coupling is sufficient to explain the
small effects observed in Nb-doped SrTiO3 . These results clarify contradicting
transport interpretations in SrTiO3 -based heterostructures.Comment: 5 pages, 5 figure
Scanning SQUID Susceptometry of a paramagnetic superconductor
Scanning SQUID susceptometry images the local magnetization and
susceptibility of a sample. By accurately modeling the SQUID signal we can
determine the physical properties such as the penetration depth and
permeability of superconducting samples. We calculate the scanning SQUID
susceptometry signal for a superconducting slab of arbitrary thickness with
isotropic London penetration depth, on a non-superconducting substrate, where
both slab and substrate can have a paramagnetic response that is linear in the
applied field. We derive analytical approximations to our general expression in
a number of limits. Using our results, we fit experimental susceptibility data
as a function of the sample-sensor spacing for three samples: 1) delta-doped
SrTiO3, which has a predominantly diamagnetic response, 2) a thin film of
LaNiO3, which has a predominantly paramagnetic response, and 3) a
two-dimensional electron layer (2-DEL) at a SrTiO3/AlAlO3 interface, which
exhibits both types of response. These formulas will allow the determination of
the concentrations of paramagnetic spins and superconducting carriers from fits
to scanning SQUID susceptibility measurements.Comment: 11 pages, 13 figure
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