We report the observation of an unusual B dependence of transverse magnetoresistance (MR) in the PrFeAsO, one of the parent compound of pnictide superconductors. Below the spin density wave transition, MR is large, positive and increases with decreasing temperature. At low temperatures, MR increases linearly with B up to 14 T. For T ≥40 K, MR vs B curve develops a weak curvature in the low-field region which indicates a crossover from B linear to B 2 dependence as B→0. The B linear MR originates from the Dirac cone states and has been explained by the quantum mechanical model proposed by Abrikosov.The Fe-pnictide high-temperature superconductors have attracted much interest because of the interplay of multi-band structure of Fermi surface and antiferromagnetism mediated by the magnetic Fe ions 1 . The undoped compounds RFeAsO (R=La, Ce, Pr, Nd and Sm) and AFe 2 As 2 (A=Ba, Ca, Sr, Eu) are semimetal and exhibit a structural phase transition at T S followed by an antiferromagnetic spin-density wave (SDW) magnetic ordering at T N 2 . This SDW has been argued to arise from Fermi surface nesting of the hole and electron Fermi surface sheets, and/or from one-electron band effects 3 . The theoretical calculation shows that the combination of the physical symmetry and topology of the band structure naturally stabilizes a gapless nodal SDW state with Dirac nodes for the parent compounds of pnictide 4,5 . Angle-resolved photoemission spectroscopy measurement on BaFe 2 As 2 confirms a Dirac-type dispersion in the antiferromagnetic phase 6 .Dirac type dispersion was first observed in graphene, where the energy spectrum is linear in momentum at the corners of the first Brillouin zone, so that the electrons at low energies can be described by the Dirac equation 7,8 . Such a unique energy band structure gives rise to several characteristic transport properties 9 . In this letter, we report the investigation on the magnetotransport properties of PrFeAsO sample, one of the parent compound of 1111 oxypnictides. We observe a large positive magnetoresistance (MR) below the SDW transition temperature. At low temperature, the MR follows a linear field dependence up to 14 T magnetic field. For T ≥40 K, MR vs B curve develops a weak curvature in the lowfield region which indicates a crossover from B linear to B 2 dependence. The B linear dependence of MR is analyzed by the quantum mechanical model developed by Abrikosov 10,11 .Polycrystalline PrFeAsO sample has been prepared by standard solid state reaction method as described in our a) Electronic mail: dilipkumar.bhoi@saha.ac.in b) Electronic mail: prabhat.mandal@saha.ac.in earlier reports 12 . The phase purity of the sample was checked by powder X-ray diffraction method and no trace of the impurity phase has been detected. The scanning electron microscope (SEM) (SUPRA, 35 VP, Carl Zeiss) image reveals well connected platelet crystallites. The energy dispersive X-ray spectra obtained from grains of different size and morphology reveal that the stoichiometric ratio Pr:Fe:As:O is close t...
The thermodynamic properties of ternary liquid Cu-Mg-Si alloys with a constant concentration ratio of x Cu /x Si ϭ 7/3 were determined using a combination of different experimental methods. Enthalpies of mixing were measured by isoperibolic calorimetry, and magnesium vapor pressures were obtained by an isopiestic method. Partial thermodynamic properties of magnesium were derived from the vapor pressure data, and the composition dependence of the magnesium activities is given for 1173 K. Integral Gibbs energies of mixing for liquid alloys were calculated by a Gibbs-Duhem integration. The agreement of the thermodynamic data obtained from different methods was found to be very good.
Alcohol route is being adopted for cleaning sodium from sodium-wetted small components of coolant circuits of fast reactors. For better understanding of sodium-alcohol reactions and their energetics, the data on thermo-chemical properties such as heats of sodium-alcohol reactions, heats of dissolution, heat capacities, thermal decomposition behaviour, etc of their end products are essential. In order to generate such data, high purity sodium alkoxides, viz. sodium methoxide, sodium ethoxide and sodium n-propoxide, were prepared by reacting sodium metal with respective alcohol. These compounds were characterized using X-ray diffraction technique and IR spectroscopy. The elemental analysis was carried out by CHNS analyser and atomic emission spectroscopy. Normal chain sodium alkoxides were found to exhibit tetragonal crystal structure. Crystal structures of sodium ethoxide and sodium n-propoxide are reported for the first time. The IR spectrum of sodium n-propoxide is also reported for the first time.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.