275 research outputs found
Coherent spin transport through a 350-micron-thick Silicon wafer
We use all-electrical methods to inject, transport, and detect spin-polarized
electrons vertically through a 350-micron-thick undoped single-crystal silicon
wafer. Spin precession measurements in a perpendicular magnetic field at
different accelerating electric fields reveal high spin coherence with at least
13pi precession angles. The magnetic-field spacing of precession extrema are
used to determine the injector-to-detector electron transit time. These transit
time values are associated with output magnetocurrent changes (from in-plane
spin-valve measurements), which are proportional to final spin polarization.
Fitting the results to a simple exponential spin-decay model yields a
conduction electron spin lifetime (T1) lower bound in silicon of over 500ns at
60K.Comment: Accepted in PR
How Good Is the Samaritan, and Why?
What is the extent and nature of religious prosociality? If religious prosociality exists, is it parochial and extended selectively to co-religionists, or is it generalized regardless of the recipient? Further, is it driven by preferences to help others or by expectations of reciprocity? We examined how much of a $0.30 bonus Mechanical Turk workers would share with the other player whose religion was prominently displayed during two online resource allocation games. In one game (but not the other), the recipient could choose to reciprocate. Results from both games showed that the more central religion was in participantsâ lives, the more of the bonus they shared, regardless of whether they were giving to atheists or Christians. Furthermore, this effect was most clearly related to self-reported frequency of âthinking about religious ideasâ, rather than belief in God or religious practice/experience. Our findings provide evidence of generalized religious prosociality and illuminate its basis
Detecting Electronic States at Stacking Faults in Magnetic Thin Films by Tunneling Spectroscopy
Co islands grown on Cu(111) with a stacking fault at the interface present a
conductance in the empty electronic states larger than the Co islands that
follow the stacking sequence of the Cu substrate. Electrons can be more easily
injected into these faulted interfaces, providing a way to enhance transmission
in future spintronic devices. The electronic states associated to the stacking
fault are visualized by tunneling spectroscopy and its origin is identified by
band structure calculations.Comment: 4 pages, 4 figures; to be published in Phys. Rev. Lett (2000
Epitaxial Co2Cr0.6Fe0.4Al thin films and magnetic tunneling junctions
Epitaxial thin films of the theoretically predicted half metal
Co2Cr0.6Fe0.4Al were deposited by dc magnetron sputtering on different
substrates and buffer layers. The samples were characterized by x-ray and
electron beam diffraction (RHEED) demonstrating the B2 order of the Heusler
compound with only a small partition of disorder on the Co sites. Magnetic
tunneling junctions with Co2Cr0.6Fe0.4Al electrode, AlOx barrier and Co counter
electrode were prepared. From the Julliere model a spin polarisation of
Co2Cr0.6Fe0.4Al of 54% at T=4K is deduced. The relation between the annealing
temperature of the Heusler electrodes and the magnitude of the tunneling
magnetoresistance effect was investigated and the results are discussed in the
framework of morphology and surface order based of in situ STM and RHEED
investigations.Comment: accepted by J. Phys. D: Appl. Phy
Spin injection and spin accumulation in all-metal mesoscopic spin valves
We study the electrical injection and detection of spin accumulation in
lateral ferromagnetic metal-nonmagnetic metal-ferromagnetic metal (F/N/F) spin
valve devices with transparent interfaces. Different ferromagnetic metals,
permalloy (Py), cobalt (Co) and nickel (Ni), are used as electrical spin
injectors and detectors. For the nonmagnetic metal both aluminium (Al) and
copper (Cu) are used. Our multi-terminal geometry allows us to experimentally
separate the spin valve effect from other magneto resistance signals such as
the anomalous magneto resistance (AMR) and Hall effects. We find that the AMR
contribution of the ferromagnetic contacts can dominate the amplitude of the
spin valve effect, making it impossible to observe the spin valve effect in a
'conventional' measurement geometry. In a 'non local' spin valve measurement we
are able to completely isolate the spin valve signal and observe clear spin
accumulation signals at T=4.2 K as well as at room temperature (RT). For
aluminum we obtain spin relaxation lengths (lambda_{sf}) of 1.2 mu m and 600 nm
at T=4.2 K and RT respectively, whereas for copper we obtain 1.0 mu m and 350
nm. The spin relaxation times tau_{sf} in Al and Cu are compared with theory
and results obtained from giant magneto resistance (GMR), conduction electron
spin resonance (CESR), anti-weak localization and superconducting tunneling
experiments. The spin valve signals generated by the Py electrodes (alpha_F
lambda_F=0.5 [1.2] nm at RT [T=4.2 K]) are larger than the Co electrodes
(alpha_F lambda_F=0.3 [0.7] nm at RT [T=4.2 K]), whereas for Ni (alpha_F
lambda_F<0.3 nm at RT and T=4.2 K) no spin signal is observed. These values are
compared to the results obtained from GMR experiments.Comment: 16 pages, 12 figures, submitted to PR
Social physique anxiety and physical activity in early adolescent girls : the influence of maturation and physical activity motives
This study considered the influence of maturation on social physique anxiety (SPA), the relationship between SPA and current and future physical activity (PA) levels and the influence of motives for physical activity on this relationship in early adolescent girls (n=162; mean age=11.80±0.33 years). Participants completed the Pubertal Development Scale, the modified Social Physique Anxiety Scale and the Motives for Physical Activity Scale at baseline and the Physical Activity Questionnaire for Older Children at baseline and 6 months later. The girls became less active across the 6 months and girls in the early stages of maturation had significantly lower SPA than the girls in the middle and late stages of maturation. SPA was not related to current or future physical activity in the sample as a whole. Cluster analysis identified four groups with different motive profiles and the High Appearance and Fitness group demonstrated a moderate negative relationship between SPA and PA at phase 1, whereas the other groups did not. These findings indicate that SPA may increase with maturation and the relationship between SPA and PA is dependent on reasons for being active. For girls who are motivated to be active primarily by body-related reasons SPA is likely to lead to lower levels of PA
Spin battery operated by ferromagnetic resonance
Precessing ferromagnets are predicted to inject a spin current into adjacent
conductors via Ohmic contacts, irrespective of a conductance mismatch with, for
example, doped semiconductors. This opens the way to create a pure spin source
spin battery by the ferromagnetic resonance. We estimate the spin current and
spin bias for different material combinations.Comment: The estimate for the magnitude of the spin bias is improved. We find
that it is feasible to get a measurable signal of the order of the microwave
frequency already for moderate rf intensitie
Reduction of the Three Dimensional Schrodinger Equation for Multilayered Films
In this paper, we present a method for reducing the three dimensional
Schrodinger equation to study confined metallic states, such as quantum well
states, in a multilayer film geometry. While discussing some approximations
that are employed when dealing with the three dimensionality of the problem, we
derive a one dimensional equation suitable for studying such states using an
envelope function approach. Some applications to the Cu/Co multilayer system
with regard to spin tunneling/rotations and angle resolved photoemission are
discussed.Comment: 14 pages, 1 figur
Quasiparticle dynamics in ferromagnetic compounds of the Co-Fe and Ni-Fe systems
We report a theoretical study of the quasiparticle lifetime and the
quasiparticle mean free path caused by inelastic electron-electron scattering
in ferromagnetic compounds of the Co-Fe and Ni-Fe systems. The study is based
on spin-polarized calculations, which are performed within the
approximation for equiatomic and Co- and Ni-rich compounds, as well as for
their constituents. We mainly focus on the spin asymmetry of the quasiparticle
properties, which leads to the spin-filtering effect experimentally observed in
spin-dependent transport of hot electrons and holes in the systems under study.
By comparing with available experimental data on the attenuation length, we
estimate the contribution of the inelastic mean free path to the latter.Comment: 10 pages, 10 figure
Theory of electrical spin injection: Tunnel contacts as a solution of the conductivity mismatch problem
Theory of electrical spin injection from a ferromagnetic (FM) metal into a
normal (N) conductor is presented. We show that tunnel contacts (T) can
dramatically increase spin injection and solve the problem of the mismatch in
the conductivities of a FM metal and a semiconductor microstructure. We also
present explicit expressions for the spin-valve resistance of FM-T-N- and
FM-T-N-T-FM-junctions with tunnel contacts at the interfaces and show that the
resistance includes both positive and negative contributions (Kapitza
resistance and injection conductivity, respectively).Comment: 4 pages, to appear in Phys. Rev. B (rapid communications
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