2,621 research outputs found
Antiferromagnetism at the YBa2Cu3O7 / La2/3Ca1/3MnO3 interface
The magnetic properties of a series of YBa2Cu3O7-x/La2/3Ca1/3MnO3
(YBCO/LC1/3MO) superlattices grown by dc sputtering at high oxygen pressures
(3.5 mbar) show the expected ferromagnetic behaviour. However, field cooled
hysteresis loops at low temperature show the unexpected existence of exchange
bias, effect associated with the existence of ferromagnetic/antiferromagnetic
(F/AF) interfaces. The blocking temperature (TB) is found thickness dependent
and the exchange bias field (HEB) is found inversely proportional to the FM
layer thickness, as expected. The presence of an AF material is probably
associated to interface disorder and Mn valence shift towards Mn4+.Comment: 12 pages, 2 figures, 1 table, submitted to Applied Physics Letter
Strong Enhancement of the Critical Current at the Antiferromagnetic Transition in ErNi2B2C Single Crystals
We report on transport and magnetization measurements of the critical current
density Jc in ErNi2B2C single crystals that show strongly enhanced vortex
pinning at the Neel temperature TN and low applied fields. The height of the
observed Jc peak decreases with increasing magnetic field in clear contrast
with that of the peak effect found at the upper critical field. We also
performed the first angular transport measurements of Jc ever conducted on this
compound. They reveal the correlated nature of this pinning enhancement, which
we attribute to the formation of antiphase boundaries at TN.Comment: 3 figure
Superficial brachioradial artery (radial artery originating from the axillary artery): a case report and embryological background
A case of anomalous terminal branching of the axillary artery, concerning the
variant called superficial brachioradial artery (arteria brachioradialis superficialis)
was described, with special regard to its embryological origin. The left
upper limb of a male cadaver was dissected in successive steps from the
axillary fossa distally to the palmar region. A variant artery, stemming from
the end of the third segment of the axillary artery, followed a superficial
course distally. It skipped the cubital fossa, ran on the lateral side of the
forearm, crossed ventrally to the palm, and terminated in the deep palmar
arch. This vessel is a case of so-called “brachioradial artery” (inexactly called
a “radial artery with a high origin”). The origin of the brachioradial artery
directly from the axillary artery belongs to the rare variants of the arterial
pattern of the upper limb. Its incidence is approximately 3%. Moreover, this
vascular variant was associated with another one concerning the brachial
plexus. The medial cutaneous nerve of the forearm joined the median nerve
in the middle third of the arm and ran further distally as a common trunk, as
the normal median nerve does. Anatomical knowledge of the axillary region
is crucial for radiodiagnostic and surgical procedures, especially in cases of
trauma. The superficially located artery brings an elevated risk of bleeding
complications in unexpected situations
Magnetic Excitations of the Diagonal Incommensurate Phase in Lightly-Doped La2-xSrxCuO4
We present inelastic neutron scattering experiments on a single-domain
crystal of lightly-doped La1.96Sr0.04CuO4. We find that the magnetic excitation
spectrum in this insulating phase with a diagonal incommensurate spin
modulation is remarkably similar to that in the superconducting regime, where
the spin modulation is bond parallel. In particular, we find that the
dispersion slope at low energy is essentially independent of doping and
temperature over a significant range. The energy at which the excitations cross
the commensurate antiferromagnetic wave vector increases roughly linearly with
doping through the underdoped regime.Comment: 4 pages, 5 figure
Levantamento semidetalhado dos solos da microbacia dos Córregos Barroso/Barrozinho no Município de Camapuã, MS.
O objetivo principal é avaliar o desgaste físico causado pela erosão hídrica nesta microbacia sob as condições atuais de uso do solo, medindo-se a quantidade de solo arrastado pelas águas de chuvas anualmente, através do monitoramento e fornecer subsídios para atenuar as perdas ou impedir o desgaste dos solos na área.bitstream/CNPS/11832/1/doc49_2002_barroso_barrozinho.pd
Electron doping evolution of the neutron spin resonance in NaFeCoAs
Neutron spin resonance, a collective magnetic excitation coupled to
superconductivity, is one of the most prominent features shared by a broad
family of unconventional superconductors including copper oxides, iron
pnictides, and heavy fermions. In this work, we study the doping evolution of
the resonances in NaFeCoAs covering the entire superconducting
dome. For the underdoped compositions, two resonance modes coexist. As doping
increases, the low-energy resonance gradually loses its spectral weight to the
high-energy one but remains at the same energy. By contrast, in the overdoped
regime we only find one single resonance, which acquires a broader width in
both energy and momentum, but retains approximately the same peak position even
when drops by nearly a half compared to optimal doping. These results
suggest that the energy of the resonance in electron overdoped
NaFeCoAs is neither simply proportional to nor the
superconducting gap, but is controlled by the multi-orbital character of the
system and doped impurity scattering effect.Comment: accepted by PR
Scaling properties of the critical behavior in the dilute antiferromagnet Fe(0.93)Zn(0.07)F2
Critical scattering analyses for dilute antiferromagnets are made difficult
by the lack of predicted theoretical line shapes beyond mean-field models.
Nevertheless, with the use of some general scaling assumptions we have
developed a procedure by which we can analyze the equilibrium critical
scattering in these systems for H=0, the random-exchange Ising model, and, more
importantly, for H>0, the random-field Ising model. Our new fitting approach,
as opposed to the more conventional techniques, allows us to obtain the
universal critical behavior exponents and amplitude ratios as well as the
critical line shapes. We discuss the technique as applied to
Fe(0.93)Zn(0.07)F2. The general technique, however, should be applicable to
other problems where the scattering line shapes are not well understood but
scaling is expected to hold.Comment: 17 pages, 5 figure
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