Magnetic Properties of Bismuth Ferrite Nanopowder Obtained by Mechanochemical Synthesis

Multiferroic bismuth ferrite (BiFeO3) nanopowders have been obtained in room temperature by mechanical synthesis. Depending on the post-synthesis processing the nanopowders have exhibited differences in the mean sizes, presence of amorphous layer and/or secondary phases. Extended magnetic study performed for fresh, annealed and hot-pressed nanopowders have revealed substantial improvement of the magnetic properties in the as-prepared powder.Comment: 4 pages, 3 figure

Electrodynamics of the vortex lattice in untwinned YBaCuO by complex impedance measurements

We report complex impedance measurements in an untwinned YBaCuO crystal. Our broad frequency range covers both the quasi static response and the resistive response of the vortex lattice. It allow us to characterize the irreversibility line without the need of any frequency dependent pinning parameters. We confirm the validity of the two modes model of vortex dynamic, and extract both the surface critical current and the flux flow resistivity around the first order transition $T_{m}$. This latter is identified by the abrupt loss of pinning and by an unexpected step of $\rho_{ff}(T)$ at $T_{m}$.Comment: accepted for publication in EPJ

Superconductivity in the Mo_2Re_3B compound

We report on the synthesis and on basic superconducting properties of a completely new Mo_2Re_3B ternary boride. The crystal structure of the Mo_2Re_3B compound is characterised by Pmmm space group and the cell parameters: a=11.626 A, b=8.465 A and c=8.026 A. The critical temperature is Tc=8.5 K, whereas the lower and the upper-critical fields at zero temperature are equal to Hc1(0)=19.2 mT and to Hc2(0)=3.7 T, respectively. The corresponding Ginzburg-Landau parameter is equal to k=16.5 and the superconducting gap is estimated to be 2delta/kTc=3.2.Comment: 17 pages, 5 figure

Upper critical field for cobalt oxide superconductors

Motivated by the recent discovery of the cobalt oxide superconductors, we calculate the temperature dependence of the upper critical field on a triangular lattice. Using the lattice version of the Gor'kov equations we investigate how the applied magnetic field affects singlet and triplet types of superconductivity. We show that in a wide range of model parameters not only Zeeman coupling, but also the diamagnetic pair breaking mechanism favors the triplet pairing. In the cobalt oxide superconductors the symmetry of the order parameter remains an open problem and both singlet and triplet superconductivity should be taken into account. We show that in such a case, an external magnetic field may induce a transition from singlet to triplet superconductivity. We discuss experimental results which may confirm this tempting hypothesis

My grade, my right: linking academic entitlement to academic performance

The identifcation of determinants and correlates of academic entitlement is of particular interest for researchers and (academic) tutors alike. Whilst personality traits have been linked to academic entitlement in the past, the relative importance of familial influence remains unclear. Hence, to address this deficit, this study utilizes a sample of business and psychology undergraduates (N=170) in the United Arab Emirates. Additionally, the impact of academic entitlement on students’ misestimation of coursework grades was assessed in a subsample of psychology undergraduates (N=92). Multiple regression analyses revealed honesty–humility as the strongest predictor of academic entitlement, indicating lower entitlement of more honest students. In contrast, familial influences were unrelated to academic entitlement. Interestingly, higher entitled expectations were associated with larger overestimation of grades. Our findings indicate honesty–humility as an important driver of academic entitlement, whilst entitled expectations appear to be associated with misperceptions of students' own academic performance

Possible singlet to triplet pairing transition in NaxCoO2 H2O

We present precise measurements of the upper critical field (Hc2) in the recently discovered cobalt oxide superconductor. We have found that the critical field has an unusual temperature dependence; namely, there is an abrupt change of the slope of Hc2(T) in a weak field regime. In order to explain this result we have derived and solved Gor'kov equations on a triangular lattice. Our experimental results may be interpreted in terms of the field-induced transition from singlet to triplet superconductivity.Comment: 6 pages, 5 figures, revte