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Enhanced superconductivity of FeSe in the 2D limit on oxide surfaces as well as the prediction of topological superconductivity at the interface to topological insulators makes the fabrication of Fe-chalcogenide monolayers a topic of current interest. So far superconductive properties of the latter are mostly studied by scanning tunneling spectroscopy, which can detect gaps in the local density of states as an indicator for Cooper pairing. Direct macroscopic transport properties, which can prove or falsify a true superconducting phase, are yet widely unexplored due to the difficulty to grow monolayer films with homogeneous material properties on a larger scale. Here we report on a promising route to fabricate micron-scale continuous carpets of monolayer thick FeSe on Bi2Se3 topological insulators. In contrast to previous procedures based on ultraflat bulk Bi2Se3 surfaces, we use molecular beam epitaxy grown Bi2Se3 films with high step-edge densities (terrace widths 10–100 nm). We observe that step edges promote the almost strainless growth of coalescing FeSe domains without compromising the underlying Bi2Se3 crystal structure. [ABSTRACT FROM AUTHOR]

We report on the evolution of magnetic properties in the PrNii1-xCux Al series investigated by measurements of magnetization, AC susceptibility, specific heat, and powder neutron diffraction. For compounds with a low Cu content, we observe antiferromagnetic incommensurate structures characterized by propagation vector k = (1/20?) having q = 0.416 ± 0.002 and 0.428 ± 0.006 in the case oi χ = 0.1 and 0.2, respectively. A commensurate antiferromagnetic structure with k = (1/20 1/2) then appears in compounds with χ = 0.4 and 0.5, which is followed by a spin-glass state with short-range correlations in the Cu-rich part of the series. The short-range magnetic correlations have an antiferromagnetic character with a propagation vector close to the one observed in the magnetically ordered PrCuAl. Investigations of the spin relaxation phenomena by use of the frequency-dependent AC susceptibility revealed that a spin-glass-hke state develops at low temperatures with evidence of collective clustering. A crystal-field energy scheme, deduced from specific heat data, is characterized by a quasidoublet ground state in the whole series. [ABSTRACT FROM AUTHOR]

Single crystals of YbPt2Si2 and Yb2Pt3Si5 have been prepared by solvent growth method with Sn flux, characterized by X-ray diffraction and by EDX microprobe analysis and investigated by measurement of magnetization, specific heat and electrical resistivity as functions of temperature and magnetic field. YbPt2Si2 (Yb2Pt3Si5) crystalizes in the tetragonal CaBe2Ge2-type (orthorhombic U2Co3Si5-type) structure. Both compounds exhibit metallic resistivity behavior without visible anomaly, which could be connected with onset of magnetic ordering. Neither the specific heat shows any sign of magnetic ordering down to 0.5 K. The corresponding temperature dependences of the magnetic susceptibility of both compounds behave qualitatively similar, which is reminiscent of spin fluctuation behavior: a broad maximum at high temperatures, a shallow minimum at lower temperatures, followed by an upturn with further cooling the crystal, which can be suppressed by applying a sufficient magnetic field. The rather low values of the γ-coefficients of the specific heat (~ 25 ÷ 35 mJ∙mol∙K-2) do not support the mixed valence scenario discussed in literature for YbPt2Si2. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of PrNi1-xCuxAl series were studied by X-ray diffraction, magnetization and specific heat. The hexagonal ZrNiAl-type structure is preserved in the whole series. Compounds with x up to 0.4 order antiferromagnetically with the Néel temperatures between 3 and 5 K. The rest of the compounds (x = 0.5-0.9) exhibits a transition into a spin glass state below the freezing temperatures around 4 K. The analysis of the specific heat data reveals a quasi-doublet ground state well separated from higher crystal field levels in the whole series. [ABSTRACT FROM AUTHOR]

The electronic structure of thin films of FeTe grown on Bi 2 Te 3 is investigated using angle-resolved photoemission spectroscopy, scanning tunneling microscopy and first principles calculations. As a comparison, data from cleaved bulk Fe 1.08 Te taken under the same experimental conditions is also presented. Due to the substrate and thin film symmetry, FeTe thin films grow on Bi 2 Te 3 in three domains, rotated by 0°, 120°, and 240°. This results in a superposition of photoemission intensity from the domains, complicating the analysis. However, by combining bulk and thin film data, it is possible to partly disentangle the contributions from three domains. We find a close similarity between thin film and bulk electronic structure and an overall good agreement with first principles calculations, assuming a p-doping shift of 65 meV for the bulk and a renormalization factor of around two. By tracking the change of substrate electronic structure upon film growth, we find indications of an electron transfer from the FeTe film to the substrate. No significant change of the film's electronic structure or doping is observed when alkali atoms are dosed onto the surface. This is ascribed to the film's high density of states at the Fermi energy. This behavior is also supported by the ab initio calculations.