Electronic structure of REREAuMg and REREAgMg (RERE = Eu, Gd, Yb)

We have investigated the electronic structure of the equiatomic EuAuMg, GdAuMg, YbAuMg and GdAgMg intermetallics using x-ray photoelectron spectroscopy. The spectra revealed that the Yb and Eu are divalent while the Gd is trivalent. The spectral weight in the vicinity of the Fermi level is dominated by the mix of Mg $s$, Au/Ag $sp$ and $RE$ $spd$ bands, and not by the $RE$ $4f$. We also found that the Au and Ag $d$ bands are extraordinarily narrow, as if the noble metal atoms were impurities submerged in a low density $sp$ metal host. The experimental results were compared with band structure calculations, and we found good agreement provided that the spin-orbit interaction in the Au an Ag $d$ bands is included and correlation effects in an open $4f$ shell are accounted for using the local density approximation + Hubbard $U$ scheme. Nevertheless, limitations of such a mean-field scheme to explain excitation spectra are also evident.Comment: 4 pages, 3 figures, Brief Repor

Magnetoresistance, specific heat and magnetocaloric effect of equiatomic rare-earth transition-metal magnesium compounds

We present a study of the magnetoresistance, the specific heat and the magnetocaloric effect of equiatomic $RET$Mg intermetallics with $RE = {\rm La}$, Eu, Gd, Yb and $T = {\rm Ag}$, Au and of GdAuIn. Depending on the composition these compounds are paramagnetic ($RE = {\rm La}$, Yb) or they order either ferro- or antiferromagnetically with transition temperatures ranging from about 13 to 81 K. All of them are metallic, but the resistivity varies over 3 orders of magnitude. The magnetic order causes a strong decrease of the resistivity and around the ordering temperature we find pronounced magnetoresistance effects. The magnetic ordering also leads to well-defined anomalies in the specific heat. An analysis of the entropy change leads to the conclusions that generally the magnetic transition can be described by an ordering of localized $S=7/2$ moments arising from the half-filled $4f^7$ shells of Eu$^{2+}$ or Gd$^{3+}$. However, for GdAgMg we find clear evidence for two phase transitions indicating that the magnetic ordering sets in partially below about 125 K and is completed via an almost first-order transition at 39 K. The magnetocaloric effect is weak for the antiferromagnets and rather pronounced for the ferromagnets for low magnetic fields around the zero-field Curie temperature.Comment: 12 pages, 7 figures include

An assessment of the psychometric properties of the Brief Sensation Seeking Scale and its prediction in safety performance in a Portuguese adult sample

This study aims to present the psychometric properties of the Brief Sensation Seeking Scale in a Portuguese sample. Three studies were performed: the first study provides psychometric evidence pertaining to its reliability and factor structure, an analysis of the measurement invariance of the BSSS across gender and age, and an examination of the differences scores on the scale regarding gender, age and marital status (n = 526); the second study consists of an assessment of convergent, discriminant and postdictive validity (n = 240); and the third study includes a test-retest of the BSSS (n = 72). A four-factor model yielded the best fit to the data with good reliability and validity. The scale showed non-invariance between genders and between ages, which makes it less generalizable and susceptible to different populations. Convergent validity with the variables risk taking, need for arousal and extraversion, and discriminant validity between neuroticism, agreeableness and conscientiousness, were demonstrated. The scale presents good temporal stability and represent an important tool for psychological assessment of personality and behavior, and as a predictor of safety performance.FCTFoundation for Science and TechnologyPortuguese Foundation for Science and Technology [UID/SOC/04020/2013