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 NaFe1−x_{1-x}Cox_{x}As

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 NaFe$_{1-x}$Co$_x$As 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 $T_c$ drops by nearly a half compared to optimal doping. These results suggest that the energy of the resonance in electron overdoped NaFe$_{1-x}$Co$_x$As is neither simply proportional to $T_c$ 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