481 research outputs found
Presence of 3d Quadrupole Moment in LaTiO3 Studied by 47,49Ti NMR
Ti NMR spectra of LaTiO3 are reexamined and the orbital state of this
compound is discussed. The NMR spectra of LaTiO3 taken at 1.5 K under zero
external field indicate a large nuclear quadrupole splitting. This splitting is
ascribed to the presence of the rather large quadrupole moment of 3d electrons
at Ti sites, suggesting that the orbital liquid model proposed for LaTiO3 is
inappropriate. The NMR spectra are well explained by the orbital ordering model
expressed approximately as originating from
a crystal field effect. It is also shown that most of the orbital moment is
quenched.Comment: 4 pages, 3 fugures; to appear in Phys. Rev. Let
Tuning the electrically evaluated electron Lande g factor in GaAs quantum dots and quantum wells of different well widths
We evaluate the Lande g factor of electrons in quantum dots (QDs) fabricated
from GaAs quantum well (QW) structures of different well width. We first
determine the Lande electron g factor of the QWs through resistive detection of
electron spin resonance and compare it to the enhanced electron g factor
determined from analysis of the magneto-transport. Next, we form laterally
defined quantum dots using these quantum wells and extract the electron g
factor from analysis of the cotunneling and Kondo effect within the quantum
dots. We conclude that the Lande electron g factor of the quantum dot is
primarily governed by the electron g factor of the quantum well suggesting that
well width is an ideal design parameter for g-factor engineering QDs
Strategic locus for the activation of the superoxide dismutase gene in the nephron
Strategic locus for the activation of the superoxide dismutase gene in the nephron. Upon exposure to a transient ischemia, the distal tubule of the kidney often escapes the severe damage which afflicts the proximal tubule. To ascertain whether this feature of the distal tubule is attributable to its intrinsic cellular properties, we focused on two pairs of unique tubule segments; distal versus proximal convoluted tubules in the superficial cortex and distal versus proximal straight tubules in the outer stripe of the outer medulla. These tubules were chosen because, firstly, they can be identified by morphology and immunostaining, and secondly, each pair has the same anatomical relationship to the circulation. Detailed morphometric analyses were performed six hours following unilateral transient ischemia in adult rats to semiquantitate the local tissue damage in these specific nephron segments. The architecture of the distal convoluted and straight tubules was remarkably well preserved, contrasting to the moderate to extensive necrotic changes seen in the proximal tubules. In search of the potential intrinsic cellular mechanism that underlies the observed difference, we examined the segmental distribution along the nephron of manganese superoxide dismutase gene transcripts by in situ hybridization. This antioxidant enzyme gene was expressed primarily in the distal tubules with contrastingly low levels of expression in the proximal tubules. Moreover, following ischemia-reperfusion, this distal tubule-dominant pattern was further accentuated immediately following reperfusion. The study indicates that the marked difference between the proximal and distal tubules in their susceptibility to injury in vivo is attributable to their intrinsic cellular properties, which include the local level of antioxidants
Scaling of the anomalous Hall effect in SrCaRuO
The anomalous Hall effect (AHE) of ferromagnetic thin films of
SrCaRuO (0 0.4) is studied as a function of
and temperature . As increases, both the transition temperature
and the magnetization are reduced and vanish near 0.7. For all
compositions, the transverse resistivity varies non-monotonously
with , and even changes sign, thus violating the conventional expression
( is the magnetic induction, while
and are the ordinary and anomalous Hall coefficients). From the rather
complicated data of , we find a scaling behavior of the transverse
conductivity with , which is well reproduced by the
first-principles band calculation assuming the intrinsic origin of the AHE.Comment: REVTeX 4 style; 5 pages, 3 figures; revised 23/2 and accepted for
publicatio
Gelatine Cavity Dynamics of High-Speed Sphere Impact
We investigate the impact and penetration of a solid sphere passing through gelatine at various impact speeds up to 143.2 m s-1 Tests were performed with several concentrations of gelatine. Impacts for low elastic Froude number Fre a ratio between inertia and gelatine elasticity, resulted in rebound. Higher Fre values resulted in penetration, forming cavities with prominent surface textures. The overall shape of the cavities resembles those observed in water-entry experiments, yet they appear in a different order with respect to increasing inertia: rebound, quasi-seal, deep-seal, shallow-seal and surface-seal. Remarkably, similar to the We – Bo phase diagram in water-entry experiments, the elastic Froude number Fre and elastic Grashof number Gre (a ratio between gravity and gelatine elasticity) classify all five different phenomena into distinguishable regimes. We find that Fre can be a good indicator to describe the cavity length H , particularly in the shallow-seal regime. Finally, the evolution of cavity shape, pinch-off depth, and lower cavity radius are investigated for different Fre values
Disorder Induced Ferromagnetism in CaRuO3
The magnetic ground state of perovskite structure CaRuO3 has been enigmatic
for decades. Here we show that paramagnetic CaRuO3 can be made ferromagnetic by
very small amounts of partial substitution of Ru by Ti. Magnetic hysteresis
loops are observed at 5 K for as little as 2% Ti substitution. Ti is
non-magnetic and isovalent with Ru, indicating that the primary effect of the
substitution is the disruption of the magnetic ground state of CaRuO3 through
disorder. The data suggest that CaRuO3 is poised at a critical point between
ferromagnetic and paramagnetic ground states
Relative contributions of lattice distortion and orbital ordering to resonant x-ray scattering in manganites
We investigated the origin of the energy splitting observed in the resonant
x-ray scattering (RXS) in manganites. Using thin film samples with controlled
lattice parameters and orbital states at a fixed orbital filling, we estimated
that the contribution of the interatomic Coulomb interaction relative to the
Jahn-Teller mechanism is insignificant and at most 0.27. This indicates that
RXS probes mainly Jahn-Teller distortion in manganites.Comment: 8 pages, 4 figure
Crystal structure, electronic, and magnetic properties of the bilayered rhodium oxide Sr3Rh2O7
The bilayered rhodium oxide Sr3Rh2O7 was synthesized by high-pressure and
high-temperature heating techniques. The single-phase polycrystalline sample of
Sr3Rh2O7 was characterized by measurements of magnetic susceptibility,
electrical resistivity, specific heat, and thermopower. The structural
characteristics were investigated by powder neutron diffraction study. The
rhodium oxide Sr3Rh2O7 [Bbcb, a = 5.4744(8) A, b = 5.4716(9) A, c = 20.875(2)
A] is isostructural to the metamagnetic metal Sr3Ru2O7, with five 4d electrons
per Rh, which is electronically equivalent to the hypothetic bilayered
ruthenium oxide, where one electron per Ru is doped into the Ru-327 unit. The
present data show the rhodium oxide Sr3Rh2O7 to be metallic with enhanced
paramagnetism, similar to Sr3Ru2O7. However, neither manifest contributions
from spin fluctuations nor any traces of a metamagnetic transition were found
within the studied range from 2 K to 390 K below 70 kOe.Comment: To be published in PR
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