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ABSTRACT This study aimed to analyze 19 isolates of Salmonella spp., from broiler litter swabs in the State of São Paulo, by typing and analyzing the detection of resistance genes associated with ESBL’s (Extended Spectrum Beta Lactamase), AMPC (C-type cephalosporinases) and carbapenemases by molecular and phenotypic techniques. A PCR microarray platform (Check and Trace by Check-Points) was used to identify the isolated serotype. The isolates were also evaluated for identification of carbapenemase genes, MCR 1-2 (colistin resistance), AmpC (C-type cephalosporins), and ESBLs (β-lactamases resistance). To identify phenotypic antibiotic resistance, the minimal inhibitory concentration (MIC) was evaluated with the antibiotics meropenem, amoxicillin, and ceftriaxone. The most prevalent serotypes identified were S. Infantis and S. Saintpaul, with a prevalence of 15.07% (3/19). Other strains identified were S. Cerro, S. Sandiego, S. Kentucky, S. Alachua, S. Javiana, S. Livingstone, S. Typhimurium, S. Heidelberg, non-enteric Salmonella, and a Salmonella not typifiable by the typing kit. All samples were negative for identifying carba resistance genes, MCR, ESBL, and AmpC. In the phenotypic profile, meropenem was the least resistant, while amoxicillin and ceftriaxone showed a high resistance pattern. The results show that phenotypic resistance is not associated with the presence of resistance genes studied here. In addition, the resistant bacteria found in MIC have resistance mechanisms not associated with the genes studied here. Additional measures must be implemented to prevent the indiscriminate use of antimicrobial agents therapeutically or as growth promoters.

ABSTRACT Brazil is the largest exporter of chicken meat and poultry farming is one of the most important productive segments, despite major losses due to the bacterium Escherichia coli, which is also a zoonotic microorganism. The objetive of this study was to isolate E. coli and to evaluate its transmissibility potential from the field to chicken meat using the Pulsed Field Gel Electrophoresis (PFGE) technique. Environmental samples (poultry litter, soil and water) were collected from broiler farms located in the South of Brazil where the majority of the Brazilian poultry production occurs. In addition, chicken meat (gizzard, heart, drumette and tulip) samples were collected from local supermarkets. As results, 47.36% of the samples were positives for E. coli. Furthermore, 10 pairs of clones of E. coli were found always in the same substrate (two water-water pairs; three soil-soil pairs and five meat-meat pairs) using PFGE. These findings suggest that certain strains of E. coli may have habitat preferences, making the transfer from one substrate type to another more difficult to occur. Moreover, since no clones were found between environmental samples and chicken meat, it is possible to imply a low risk of E. coli transmissibility throughout the chicken meat production chain.

CeCd3As3 is a rare-earth triangular-lattice antiferromagnet with large interlayer separation. Our field-dependent heat capacity measurements at dilution fridge temperatures allow us to trace the field evolution of the spin-excitation gaps throughout the antiferromagnetic and paramagnetic regions. The distinct gap evolution places strong constraints on the microscopic pseudospin model, which, in return, yields a close quantitative description of the gap behavior. This analysis provides crucial insights into the nature of the magnetic state of CeCd3As3, with a certainty regarding its stripe order and low-energy model parameters that sets a compelling paradigm for exploring and understanding the rapidly growing family of the rare-earth-based triangular-lattice systems.

SmB6 has been a well-known Kondo insulator for decades, but recently attracts extensive new attention as a candidate topological system. Studying SmB6 under pressure provides an opportunity to acquire the much-needed understanding about the effect of electron correlations on both the metallic surface state and bulk insulating state. Here we do so by studying the evolution of two transport gaps (low temperature gap El and high temperature gap Eh) associated with the Kondo effect by measuring the electrical resistivity under high pressure and low temperature (0.3 K) conditions. We associate the gaps with the bulk Kondo hybridization, and from their evolution with pressure we demonstrate an insulator-to-metal transition at ∼4 GPa. At the transition pressure, a large change in the Hall number and a divergence tendency of the electron-electron scattering coefficient provide evidence for a destruction of the Kondo entanglement in the ground state. Our results raise the new prospect for studying topological electronic states in quantum critical materials settings.

ABSTRACT This study aimed to evaluate the effect of maltodextrin on performance of chicks passed through four fasting periods. A completely randomized design was performed, consisting of three treatments (1 - control, 2 - 4% saccharose; 3-4% maltodextrin 20) and four fasting periods after hatching (0, 12, 24 and 36 hours) with four replications, totaling 1920 birds of both sexes. The studied variables were: water intake in the first 12 hours, average food intake, average body weight and real feed conversion. Data was submitted to analysis of variance and means were compared with each other by Dunnett test at 5% significance. The use of additives and imposing of different fasting periods did not influence the performance at 42 days old. Therefore, fasted chicks consumed significantly more water. At 7 days old, chicks fasted showed higher body weight and higher feed intake, however, the viability did not suffer any influence, the weight remained higher after 21days with the fast imposition and there was no influence on other variables. There was no effect of fasting on broiler chiken's performance at 42 days old. The inclusion of sucrose and maltodextrin to drinking water stimulated the chick´s water intake and provided higher viability after seven days old.

Applied pressure drives the heavy-fermion antiferromagnet CeRhIn5 toward a quantum critical point that becomes hidden by a dome of unconventional superconductivity. Magnetic fields suppress this superconducting dome, unveiling the quantum phase transition of local character. Here, we show that [Formula: see text] magnetic substitution at the Ce site in CeRhIn5, either by Nd or Gd, induces a zero-field magnetic instability inside the superconducting state. This magnetic state not only should have a different ordering vector than the high-field local-moment magnetic state, but it also competes with the latter, suggesting that a spin-density-wave phase is stabilized in zero field by Nd and Gd impurities, similarly to the case of Ce0.95Nd0.05CoIn5 Supported by model calculations, we attribute this spin-density wave instability to a magnetic-impurity-driven condensation of the spin excitons that form inside the unconventional superconducting state.

We present the results of a high-resolution valence-band photoemission spectroscopic study of SmB6 which shows evidence for a V-shaped density of states of surface origin within the bulk gap. The spectroscopy data are interpreted in terms of the existence of heavy 4f surface states, which may be useful in resolving the controversy concerning the disparate surface Fermi-surface velocities observed in experiments. Most importantly, we find that the temperature dependence of the valence-band spectrum indicates that a small feature appears at a binding energy of about -9 meV at low temperatures. We attribute this feature to a resonance caused by the spin-exciton scattering in SmB6 which destroys the protection of surface states due to time-reversal invariance and spin-momentum locking. The existence of a low-energy spin exciton may be responsible for the scattering, which suppresses the formation of coherent surface quasiparticles and the appearance of the saturation of the resistivity to temperatures much lower than the coherence temperature associated with the opening of the bulk gap.

Electron spin resonance (ESR) of diluted Nd(3+) ions in the topologically nontrivial semimetallic (TNSM) YBiPt compound is reported. The cubic YBiPt compound is a non-centrosymmetric half Heusler material which crystallizes in the F43m space group. The low temperature Nd(3+) ESR spectra showed a g-value of 2.66(4) corresponding to a Γ6 cubic crystal field Kramers' doublet ground state. Remarkably, the observed metallic and diffusive (Dysonian) Nd(3+) lineshape presented an unusual dependence with grain size, microwave power, Nd(3+) concentration and temperature. Moreover, the spin dynamic of the localized Nd(3+) ions in YBiPt was found to be characteristic of a phonon-bottleneck regime. It is claimed that, in this regime for YBiPt, phonons are responsible for mediating the diffusion of the microwave energy absorbed at resonance by the Nd(3+) ions to the thermal bath throughout the skin depth (δ ≃ μm). We argue that this is only possible because of the existence of highly mobile conduction electrons inside the skin depth of YBiPt that are strongly coupled to the phonons by spin-orbit coupling. Therefore, our unexpected ESR results point to a coexistence of metallic and insulating behaviors within the skin depth of YBiPt. This scenario is discussed in the light of the TNSM properties of this compound.

Heavy fermion (HF) materials exhibit a rich array of phenomena due to the strong Kondo coupling between their localized moments and itinerant electrons. A central question in their study is to understand the interplay between magnetic order and charge transport, and its role in stabilizing new quantum phases of matter. Particularly promising in this regard is a family of tetragonal intermetallic compounds CeTX2 (where T denotes transition metal and X denotes pnictogen), which includes a variety of HF compounds showing T-linear electronic specific heat Ce∼γT, with γ∼20-500mJmol-1K-2, reflecting an effective-mass enhancement ranging from small to modest. Here, we study the low-temperature field-tuned phase diagram of high-quality CeAgBi2 using magnetometry and transport measurements. We find an antiferromagnetic transition at TN=6.4K with weak magnetic anisotropy and the easy axis along the c axis, similar to previous reports (TN=6.1K). This scenario, along with the presence of two anisotropic Ruderman-Kittel-Kasuya-Yosida interactions, leads to a rich field-tuned magnetic phase diagram, consisting of five metamagnetic transitions of both first and second order. In addition, we unveil an anomalous Hall contribution for fields H

We report the observation of two pressure-induced quantum phase transitions in a YbB6 single crystal, i.e., from a topologically trivial semiconductor to an intermediate semimetal and then from the semimetal to a possible topologically nontrivial high-pressure gapped phase through in situ high-pressure transport and synchrotron x-ray diffraction measurements. Our high-pressure absorption results reveal that the mixed-valence state in pressurized YbB6 above 15 GPa plays an important role in the formation of the high-pressure state with a reopened gap. These high-pressure results may be helpful for shedding light on the intriguing relation between the topology and the 4f electrons in the rare-earth hexaborides.

Motivated by the presence of competing magnetic interactions in the heavy fermion family CeTX2 (T = transitionmetal, X=pnictogen), here we study the novel parent compound CeCd0.7Sb2 by combining magnetization, electrical resistivity, and heat-capacity measurements. Contrary to the antiferromagnetic (AFM) ground state observed in most members of this family, the magnetic properties of our CeCd0.7Sb2 single crystals revealed a ferromagnetic ordering at Tc=3K with an unusual soft behavior. By using a mean field model including anisotropic nearest-neighbor interactions and the tetragonal crystalline electric field (CEF) Hamiltonian, a systematic analysis of our macroscopic data was obtained. Our fits allowed us to extract a simple but very distinct CEF scheme, as compared to the AFM counterparts. As in the previously studied ferromagnet CeAgSb2, a pure |±1/2) ground state is realized, hinting at a general trend within the ferromagnetic members. More generally, we propose a scenario for the understanding of the magnetism in this family of compounds based on the subtle changes of dimensionality in the crystal structure.

In this work, we report superconductivity at 5.5 K in the new pseudo-ternary Th0.93Zr0.07B12 compound. We show clearly evidence that appropriate amounts of Zr substitution at the Th site induce the stabilization of the UB12 prototype structure at ambient pressure. The superconducting bulk properties of Th0.93Zr0.07B12 are confirmed by means of magnetization, electronic transport properties and specific heat measurements. The H-T phase diagrams based on magnetization and magnetoresistance measurements yield μ0Hc1(0)=6 mT and μ0Hc2(0)=98 mT and allow us to estimate the coherence length ξo∼57.9 nm and the penetration depth λL∼234 nm at zero kelvin.

We combine magnetization, pressure-dependent electrical resistivity, and heat capacity measurements to investigate the physical properties of the novel compound UAuBi2. Our single crystals, grown by the self-flux method, share the same tetragonal HfCuSi2-type structure as their Ce-based counterparts. UAuBi2 shows ferromagnetic ordering at Tc=22.5 K, in contrast with the antiferromagnetic transition found in CeAuBi2 (TN=12K) but closely related to UAuSb2 (Tc=31K). Despite the differences, all compounds display an easy axis of magnetization along the c axis and a large magnetocrystalline anisotropy. The heat capacity and pressure-dependent resistivity suggest that UAuBi2 exhibits moderately heavy-fermion behavior (γ∼100mJ/mol·K2) with strongly localized 5f electrons. An intricate competition between crystalline electric field (CEF) effects and two anisotropic exchange interactions (JRKKY) persists in the 5f system, which leads to the striking difference between ground states. A systematic analysis of our macroscopic data using a mean-field model including anisotropic JRKKY interactions and the tetragonal CEF Hamiltonian allows us to extract the CEF scheme and the values of JRKKY. Our results suggest a general trend in this family of compounds and shed light on the similarities and differences between 4f and 5f members.

In this work, we report superconductivity in the new ternary Ta1-xHfxB system. We also show clearly evidence that appropriate amounts of Hf substitution at the Ta site induce the stabilization of the orthorhombic FeB prototype structure in this system. Bulk superconductivity is confirmed by magnetization, electronic transport and specific heat measurements. The Hall signal has temperature dependence and the specific heat data at low temperature deviate from the conventional exponential temperature dependence in Ta0.7Hf0.3B. These results suggest multiband superconductivity in this compound.

In this work, we report superconductivity in the new ternary Ta1-xHfxB system. We also show clearly evidence that appropriate amounts of Hf substitution at the Ta site induce the stabilization of the orthorhombic FeB prototype structure in this system. Bulk superconductivity is confirmed by magnetization, electronic transport and specific heat measurements. The Hall signal has temperature dependence and the specific heat data at low temperature deviate from the conventional exponential temperature dependence in Ta0.7Hf0.3B. These results suggest multiband superconductivity in this compound.

Motivated by the interesting magnetic anisotropy found in the heavy fermion family CeTX2 (T = transition metal and X = pnictogen), here, we study the novel parent compound CeAu1-xBi2-y by combining magnetization, pressure dependent electrical resistivity, and heat-capacity measurements. The magnetic properties of our nearly stoichiometric single crystal sample of CeAu1-xBi2-y (x = 0.92 and y = 1.6) revealed an antiferromagnetic ordering at TN = 12 K with an easy axis along the c-direction. The field dependent magnetization data at low temperatures reveal the existence of a spin-flop transition when the field is applied along the c-axis (Hc ∼ 7.5 T and T = 5 K). The heat capacity and pressure dependent resistivity data suggest that CeAu0.92Bi1.6 exhibits a weak heavy fermion behavior with strongly localized Ce3+ 4f electrons. Furthermore, the systematic analysis using a mean field model including anisotropic nearest-neighbors interactions and the tetragonal crystalline electric field (CEF) Hamiltonian allows us to extract a CEF scheme and two different values for the anisotropic J RKKY exchange parameters between the Ce3+ ions in this compound. Thus, we discuss a scenario, considering both the anisotropic magnetic interactions and the tetragonal CEF effects, in the CeAu1-xBi2-y compounds, and we compare our results with the isostructural compound CeCuBi2.

We report a combined study of external pressure and Cu-substitution on BaFe2As2 single crystals grown by the in-flux technique. At ambient pressure, the Cu-substitution is known to suppress the spin density wave (SDW) phase in pure BaFe2As2(T(SDW) ≈ 140 K) and to induce a superconducting (SC) dome with a maximum transition temperature T(c)(max) ≃ 4.2 K. This T(c)(max) is much lower than the T(c) ∼ 15-28 K achieved in the case of Ru, Ni and Co substitutions. Such a lower T(c) is attributed to a Cu(2+) magnetic pair-breaking effect. The latter is strongly suppressed by applied pressure, as shown herein, Tc can be significantly enhanced by applying high pressures. In this work, we investigated the pressure effects on Cu(2+) magnetic pair-breaking in the BaFe(2-x)Cu(x)As2 series. Around the optimal concentration (x(opd) = 0.11), all samples showed a substantial increase of T(c) as a function of pressure. Yet for those samples with a slightly higher doping level (over-doped regime), T(c) presented a dome-like shape with maximum T(c) ≃ 8 K. Remarkably interesting, the under-doped samples, e.g. x = 0.02 display a maximum pressure induced T(c) ≃ 30 K which is comparable to the maximum T(c)'s found for the pure compound under external pressures. Furthermore, the magnetoresistance effect as a function of pressure in the normal state of the x = 0.02 sample also presented an evolution consistent with the screening of the Cu(2+) local moments. These findings demonstrate that the Cu(2+) magnetic pair-breaking effect is completely suppressed by applying pressure in the low concentration regime of Cu(2+) substituted BaFe2As2.

Intense efforts have been made in order to synthesize new tetragonal ternary intermetallic compounds with low-temperature ground states on the border of magnetism. Here we report the synthesis of ThCo2Sn2 single crystals, which crystallize in the tetragonal CaBe2Ge2-type structure, using the flux technique. Further investigation of the physical properties by magnetic susceptibility and pressure-dependent electrical resistivity measurements confirm the presence of antiferromagnetic ordering associated with the Co ions, but with a higher ordering temperature of TN 78 K when compared to TN 65 K of the polycrystalline counterpart. Our results show that both Cu-substitution and applied pressure up to 22 kbar are not able to induce superconductivity in this system. Nevertheless, our analyses point out to a putative quantum critical point at higher pressures.

The search for new superconductors (SC) represents an exciting field in condensed matter physics. Recently, CeNi0.8Bi2 has been reported as a new bulk SC (Tc ∼ 4.2 K) in which Ni vacancies play an essential role for the emergence of superconductivity. Here we report experiments of magnetic susceptibility and heat capacity combined with energy dispersive X- ray spectroscopy analysis on CeNixBi2-y (x 0.62, 0.70, 0.74, 0.78) single crystals. Our data show a systematic enhancement of the antiferromagnetic transition temperature (TN) with x, as well as the low temperature Ce3+ magnetic anisotropy. In particular, we find that the crystal- field ground state doublet becomes more isolated from the excited states as one approaches the Ni-rich end. As a consequence of such subtle crystal-field evolution, our analyses suggest that both the magnetic frustration and the hybridization between Ce3+ 4f and conduction electrons are decreasing along the series. In addition, SC transitions are observed in both La and Ce members with no bulk signature, strongly indicating the presence of impurity SC phases.

In this work we report the effects of hydrostatic pressure and magnetic field on the electronic transport properties of the antiferromagnetic compound Eu3Ir4Sn13 (TN ∼ 10 K). Single crystals of Eu3Ir4Sn13 were synthesized using the Sn self-flux technique. DC electrical resistivity measurements as a function of temperature were performed by means of the four- probe technique. The high-temperature anomaly at T∗ ∼ 57 K attributed to a structural distortion of the Sn1Sn212 cages in Eu3Ir4Sn13 is rapidly decreased to lower temperatures at a rate dT∗/dP 2 K/kbar, while the antiferromagnetic transition due to the Eu2+ ions is only weakly affected. Our data do not indicate any magnetoelastic effect associated with the structural instability at T∗ . Furthermore, the suppression of the lattice distortion by application of external pressure is not accompanied by the emergence of superconductivity, possibly due to strong magnetic correlations between the Eu2+ localized magnetic moments.

To investigate whether the dense Kondo compound CeB6 might evolve into a topological insulator under sufficient pressure, four-point electrical resistivity measurements have been carried out over the temperature range 1.3 K-295 K in a diamond anvil cell to 122 GPa. The temperature Tmax of the resistivity maximum initially increases slowly with pressure but disappears between 12 and 20 GPa. The marked changes observed under pressure suggest that a valence and/or structural transition may have occurred. Synchrotron x-ray diffraction measurements, however, fail to detect any change in crystal structure to 85 GPa. Although a transition into an insulating phase is not observed, this dense Kondo system is completely suppressed at 43 GPa, leaving behind what appears to be a conventional Fermi liquid metal.

In this work we combine magnetization, pressure dependent electrical resistivity, heat capacity, Cu63 nuclear magnetic resonance (NMR), and x-ray resonant magnetic scattering experiments to investigate the physical properties of the intermetallic CeCuBi2 compound. Our single crystals show an antiferromagnetic ordering at TN≃16 K and the magnetic properties indicate that this compound is an Ising antiferromagnet. In particular, the low temperature magnetization data revealed a spin-flop transition at T=5 K when magnetic fields of about 5.5 T are applied along the c axis. Moreover, the x-ray magnetic diffraction data below TN revealed a commensurate antiferromagnetic structure with propagation wave vector (0012) with the Ce3+ moments oriented along the c axis. Furthermore, our heat capacity, pressure dependent resistivity, and temperature dependent Cu63 NMR data suggest that CeCuBi2 exhibits a weak heavy fermion behavior with strongly localized Ce3+ 4f electrons. We thus discuss a scenario in which both the anisotropic magnetic interactions between the Ce3+ ions and the tetragonal crystalline electric field effects are taking into account in CeCuBi2.

We report the physical properties of EuPtIn4 single crystalline platelets grown by the In-flux technique. This compound crystallizes in the orthorhombic Cmcm structure with lattice parameters a=4.542(1)A., b=16.955(2)A. and c=7.389(1)A. Measurements of magnetic susceptibility, heat capacity, electrical resistivity, and electron spin resonance (ESR) reveal that EuPtIn4 is a metallic Curie-Weiss paramagnet at high temperatures with an effective moment of μeff≈7.8(1)μB due to divalent Eu ions. At low temperatures, antiferromagnetic (AFM) ordering is observed at TN=13.3K followed by a successive anomaly at T=12.6K. In addition, within the magnetic state, a spin-flop transition is observed with Hc~2.5T at T=1.8 K when the magnetic field is applied along the ac-plane. In the paramagnetic state, a single divalent Eu2+ Dysonian ESR line with a Korringa relaxation rate of b=4.1(2)Oe/K is observed. Interestingly, even at high temperatures, both ESR linewidth and electrical resistivity reveal a similar anisotropy. We discuss a possible common microscopic origin for the observed anisotropy in these physical quantities likely associated with an anisotropic magnetic interaction between Eu2+ 4f electrons mediated by conduction electrons. © 2014 Elsevier B.V.

Quantum oscillation measurements provide relevant information about the Fermi surface (FS) properties of strongly correlated metals. Here, we report on the Shubnikov-de Haas effect via high-field resistivity measurements of EuFe2As2 (Eu122) and BaFe2As2 (Ba122) single crystals. Although both pnictide compounds are isovalent with similar effective masses and density of states, at the Fermi level, our results reveal subtle changes in their fermiology. Remarkably, although the spin-density-wave (SDW) ordering temperature is higher in the Eu-rich end, Eu122 displays a much more isotropic and three-dimensional-like FS when compared with Ba122, in agreement with band structure calculations. Our experimental results suggest an anisotropic contribution of the Fe 3d orbitals to the FS in Ba122. We speculate that this orbital differentiation may be responsible for the suppression of the SDW phase in the FeAs-based compounds.

Quantum oscillation measurements provide relevant information about the Fermi surface (FS) properties of strongly correlated metals. Here, we report on the Shubnikov-de Haas effect via high-field resistivity measurements of EuFe2As2 (Eu122) and BaFe2As2 (Ba122) single crystals. Although both pnictide compounds are isovalent with similar effective masses and density of states, at the Fermi level, our results reveal subtle changes in their fermiology. Remarkably, although the spin-density-wave (SDW) ordering temperature is higher in the Eu-rich end, Eu122 displays a much more isotropic and three-dimensional-like FS when compared with Ba122, in agreement with band structure calculations. Our experimental results suggest an anisotropic contribution of the Fe 3d orbitals to the FS in Ba122. We speculate that this orbital differentiation may be responsible for the suppression of the SDW phase in the FeAs-based compounds.

The role of orbital differentiation on the emergence of superconductivity in the Fe-based superconductors remains an open question to the scientific community. In this investigation, we employ a suitable microscopic spin probe technique, namely Electron Spin Resonance (ESR), to investigate this issue on selected chemically substituted BaFe2As2 single crystals. As the spin-density wave (SDW) phase is suppressed, we observe a clear increase of the Fe 3d bands anisotropy along with their localization at the FeAs plane. Such an increase of the planar orbital content is interestingly independent of the chemical substitution responsible for suppressing the SDW phase. As a consequence, the magnetic fluctuations in combination with this particular symmetry of the Fe 3d bands are propitious ingredients for the emergence of superconductivity in this class of materials.

ABSTRACT For a long time, it has been said that eggshell quality decreases as eggs increase in size, but this increase is seen as the breeder age advances. Therefore, the present study aimed to evaluate the age and egg weight effect on Cobb 500 broiler breeders on eggshell quality. The quality measures tested were eggshell and mineral matter percentage, eggshell surface, shape and eggshell index, eggshell and membrane thickness and specific gravity. Eggs from 27, 31, 36, 40, 46, 48, 53, 58 and 63 week-old breeders were classified as eggs with a constant weight ranging from 63.8 ± 0.2; and eggs with increasing weight, according to age, being: 55.8g; 60g; 62.2g; 64.2g; 65.2g, 66.6g, 68.1g, 69.9g and 72.5g, respectively. The eggs weight did not influence the eggshell percentage and the specific gravity in seven of the nine tested ages, while for mineral matter in six of the nine studied ages. The shape and shell index, shell and membrane thickness are characteristics independent of egg weight. As the Cobb 500 broiler breeder age advanced, the mineral matter concentration and specific gravity maintained constant, the membrane thickness (R2>70) reduced, and other studied variables were influenced in the same way for both treatments. Thus, the eggshell quality decrease with the advancing age cannot be attributed solely to the increase of egg weight with consequent increase in the eggshell volume and the surface, but there are also age-related factors.

The possible existence of a sign-changing gap symmetry in BaFe2As2-derived superconductors (SC) has been an exciting topic of research in the last few years. To further investigate this subject we combine Electron Spin Resonance (ESR) and pressure-dependent transport measurements to investigate magnetic pair-breaking effects on BaFe1.9M0.1As2 (M = Mn, Co, Cu, and Ni) single crystals. An ESR signal, indicative of the presence of localized magnetic moments, is observed only for M = Cu and Mn compounds, which display very low SC transition temperature (Tc) and no SC, respectively. From the ESR analysis assuming the absence of bottleneck effects, the microscopic parameters are extracted to show that this reduction of Tc cannot be accounted by the Abrikosov-Gorkov pair-breaking expression for a sign-preserving gap function. Our results reveal an unconventional spin- and pressure-dependent pair-breaking effect and impose strong constraints on the pairing symmetry of these materials.

We report a combined study of hydrostatic pressure (P ≤ 25 kbar) and chemical substitution on the magnetic pair-breaking effect in Eu- and Mn-substituted BaFe2As2 single crystals. At ambient pressure, both substitutions suppress the superconducting (SC) transition temperature (Tc) of BaFe2–xCoxAs2 samples slightly under the optimally doped region, indicating the presence of a pair-breaking effect. At low pressures, an increase of Tc is observed for all studied compounds followed by an expected decrease at higher pressures. However, in the Eu dilute system, Tc further increases at higher pressure along with a narrowing of the SC transition, suggesting that a pair-breaking mechanism reminiscent of the Eu Kondo single impurity regime is being suppressed by pressure. Furthermore, Electron Spin Resonance (ESR) measurements indicate the presence of Mn2+ and Eu2+ local moments and the microscopic parameters extracted from the ESR analysis reveal that the Abrikosov–Gor'kov expression for magnetic pair-breaking in a conventional sign-preserving superconducting state cannot describe the observed reduction of Tc.

The search for new superconductors (SC) represents an exciting field in condensed matter physics. Recently, CeNi0.8Bi2 has been reported as a new bulk SC (Tc ∼ 4.2 K) in which Ni vacancies play an essential role for the emergence of superconductivity. Here we report experiments of magnetic susceptibility and heat capacity combined with energy dispersive X- ray spectroscopy analysis on CeNixBi2-y (x 0.62, 0.70, 0.74, 0.78) single crystals. Our data show a systematic enhancement of the antiferromagnetic transition temperature (TN) with x, as well as the low temperature Ce3+ magnetic anisotropy. In particular, we find that the crystal- field ground state doublet becomes more isolated from the excited states as one approaches the Ni-rich end. As a consequence of such subtle crystal-field evolution, our analyses suggest that both the magnetic frustration and the hybridization between Ce3+ 4f and conduction electrons are decreasing along the series. In addition, SC transitions are observed in both La and Ce members with no bulk signature, strongly indicating the presence of impurity SC phases.

Intense efforts have been made in order to synthesize new tetragonal ternary intermetallic compounds with low-temperature ground states on the border of magnetism. Here we report the synthesis of ThCo2Sn2 single crystals, which crystallize in the tetragonal CaBe2Ge2-type structure, using the flux technique. Further investigation of the physical properties by magnetic susceptibility and pressure-dependent electrical resistivity measurements confirm the presence of antiferromagnetic ordering associated with the Co ions, but with a higher ordering temperature of TN 78 K when compared to TN 65 K of the polycrystalline counterpart. Our results show that both Cu-substitution and applied pressure up to 22 kbar are not able to induce superconductivity in this system. Nevertheless, our analyses point out to a putative quantum critical point at higher pressures.

In this work we report the effects of hydrostatic pressure and magnetic field on the electronic transport properties of the antiferromagnetic compound Eu3Ir4Sn13 (TN ∼ 10 K). Single crystals of Eu3Ir4Sn13 were synthesized using the Sn self-flux technique. DC electrical resistivity measurements as a function of temperature were performed by means of the four- probe technique. The high-temperature anomaly at T∗ ∼ 57 K attributed to a structural distortion of the Sn1Sn212 cages in Eu3Ir4Sn13 is rapidly decreased to lower temperatures at a rate dT∗/dP 2 K/kbar, while the antiferromagnetic transition due to the Eu2+ ions is only weakly affected. Our data do not indicate any magnetoelastic effect associated with the structural instability at T∗ . Furthermore, the suppression of the lattice distortion by application of external pressure is not accompanied by the emergence of superconductivity, possibly due to strong magnetic correlations between the Eu2+ localized magnetic moments.

Single crystals of Ba 1-xEu xFe 2As 2 were studied by magnetic susceptibility, heat capacity, resistivity, and electron spin resonance (ESR) measurements. Spin-density wave (at T SDW) and antiferromagnetic (at T N) phase transitions were mapped as a function of x. For 0.2, we found a single Eu2 + ESR Dysonian line that presents an isotropic linear increase (Korringa) of its linewidth (ΔH) above T SDW which systematically decreases with decreasing x. In contrast, for a critical concentration x c (0.10

Single crystals of Ba 1-xEu xFe 2As 2 were studied by magnetic susceptibility, heat capacity, resistivity, and electron spin resonance (ESR) measurements. Spin-density wave (at T SDW) and antiferromagnetic (at T N) phase transitions were mapped as a function of x. For 0.2, we found a single Eu2 + ESR Dysonian line that presents an isotropic linear increase (Korringa) of its linewidth (ΔH) above T SDW which systematically decreases with decreasing x. In contrast, for a critical concentration x c (0.10

We present electron spin resonance (ESR) measurements in single-crystalline samples of EuIn 2As 2 grown using the In-flux method. This compound crystallizes in a hexagonal P6(3)/mmc structure and presents antiferromagnetic (AFM) ordering below T N=16 K. In the paramagnetic state, a single Eu2 + Dysonian ESR line with nearly temperature-independent g-factor and linewidth is observed, indicating the absence of Korringa-like relaxation of the Eu2 + ions. Approaching the AFM transition, we observe an anisotropic g-shift and a linewidth broadening which has a maximum at T N, suggesting that the short-range AFM correlation dominates the spin dynamics of the Eu2 + spins in this temperature range. Our results are discussed based on complementary data (magnetic susceptibility, heat capacity, and electrical resistivity measurements) that provide further details about the global macroscopic physical properties of the EuIn 2As 2 intermetallic compound. © 2012 American Physical Society.