Very large magnetoresistance in Fe0.28_{0.28}TaS2_{2} single crystals

Magnetic moments intercalated into layered transition metal dichalcogenides are an excellent system for investigating the rich physics associated with magnetic ordering in a strongly anisotropic, strong spin-orbit coupling environment. We examine electronic transport and magnetization in Fe$_{0.28}$TaS$_{2}$, a highly anisotropic ferromagnet with a Curie temperature $T_{\mathrm{C}} \sim 68.8~$K. We find anomalous Hall data confirming a dominance of spin-orbit coupling in the magnetotransport properties of this material, and a remarkably large field-perpendicular-to-plane MR exceeding 60% at 2 K, much larger than the typical MR for bulk metals, and comparable to state-of-the-art GMR in thin film heterostructures, and smaller only than CMR in Mn perovskites or high mobility semiconductors. Even within the Fe$_x$TaS$_2$ series, for the current $x$ = 0.28 single crystals the MR is nearly $100\times$ higher than that found previously in the commensurate compound Fe$_{0.25}$TaS$_{2}$. After considering alternatives, we argue that the large MR arises from spin disorder scattering in the strong spin-orbit coupling environment, and suggest that this can be a design principle for materials with large MR.Comment: 8 pages, 8 figures, accepted in PR

Pressure versus concentration tuning of the superconductivity in Ba(Fe(1-x)Cox)2As2

In the iron arsenide compound BaFe2As2, superconductivity can be induced either by a variation of its chemical composition, e.g., by replacing Fe with Co, or by a reduction of the unit-cell volume through the application of hydrostatic pressure p. In contrast to chemical substitutions, pressure is expected to introduce no additional disorder into the lattice. We compare the two routes to superconductivity by measuring the p dependence of the superconducting transition temperature Tc of Ba(Fe(1-x)Cox)2As2 single crystals with different Co content x. We find that Tc(p) of underdoped and overdoped samples increases and decreases, respectively, tracking quantitatively the Tc(x) dependence. To clarify to which extent the superconductivity relies on distinct structural features we analyze the crystal structure as a function of x and compare the results with that of BaFe2As2 under pressure.Comment: 14 pages, 4 figures, to be published in JPSJ Vol. 79 No. 12. The copyright is held by The Physical Society of Japa

Tobacco use amongst out of school adolescents in a Local Government Area in Nigeria

Abstract Introduction Out-of-school adolescents are often neglected when planning for tobacco prevention programmes whereas they are more vulnerable. Few studies exist in Nigeria about their pattern of tobacco use to serve as the basis for effective policy formulation. Method A sub sample of 215 out of school adolescents was analyzed from a descriptive cross sectional study on psychoactive substance use amongst youths in two communities in a Local Government Area in Nigeria which used a multi-stage sampling technique. Results Males were 53% and females 47%. Only 20.5% had ever used tobacco while 11.6% were current users. Males accounted for 60% of current users compared to 40% amongst females. Of current users, 84% believed that tobacco is not harmful to health. In addition, the two important sources of introduction to tobacco use were friends 72% and relatives 20%. Use of tobacco amongst significant others were: friends 27%, fathers 8.0%, relatives 4.2% and mothers 0.5%. The most common sources of supply were motor parks 52% and friends 16%. Conclusion The study showed that peer influence is an important source of introduction to tobacco use while selling of tobacco to adolescents in youth aggregation areas is common. We advocate for a theory based approach to designing an appropriate health education intervention targeted at assisting adolescents in appreciating the harmful nature of tobacco use in this locality. A point-of-sale restriction to prevent adolescent access to tobacco in youth aggregation areas within the context of a comprehensive tobacco control policy is also suggested. However, more research would be needed for an in-depth understanding of the tobacco use vulnerability of this group of adolescents.Peer Reviewe

Magnetic properties of the layered oxypnictides (LnO)MnAs (Ln = La, Ce, Pr, Nd)

We have investigated the rare earth elements dependence on the magnetism to understand the contribution to physical properties of the 4f electrons of (LnO)MnAs (Pn = La, Ce, Pr, Nd). (CeO)MnAs, (PrO)MnAs and (NdO)MnAs shows the antiferromagnetic behaviors at low temperature. (CeO)MnAs and (NdO)MnAs have the magnetic anomalies around 34 K and 24 K, respectively. So, it is speculated that the anomalies depend on the Mn -Mn distance directl