31 research outputs found
Coexistence of superconductivity and ferromagnetism in Sr0.5Ce0.5FBiS2-xSex (x = 0.5 and 1.0), a non-U material with Tc < TFM
We have carried out detailed magnetic and transport studies of the new Sr0.5Ce0.5FBiS2-xSex (0.0 ≤ x ≤ 1.0) superconductors derived by doping Se in Sr0.5Ce0.5FBiS2. Se–doping produces several effects: it suppresses semiconducting–like behavior observed in the undoped Sr0.5Ce0.5FBiS2, the ferromagnetic ordering temperature, TFM, decreases considerably from 7.5 K (in Sr0.5Ce0.5FBiS2) to 3.5 K and the superconducting transition temperature, Tc, gets enhanced slightly to 2.9–3.3 K. Thus in these Se–doped materials, TFM is marginally higher than Tc. Magnetization studies provide evidence of bulk superconductivity in Sr0.5Ce0.5FBiS2-xSex at x ≥ 0.5 in contrast to the undoped Sr0.5Ce0.5FBiS2 (x = 0) where magnetization measurements indicate a small superconducting volume fraction. Quite remarkably, as compared with the effective paramagnetic Ce–moment (~2.2 μB), the ferromagnetically ordered Ce–moment in the superconducting state is rather small (~0.1 μB) suggesting itinerant ferromagnetism. To the best of our knowledge, Sr0.5Ce0.5FBiS2-x Sex (x = 0.5 and 1.0) are distinctive Ce–based bulk superconducting itinerant ferromagnetic materials with Tc < TFM. Furthermore, a novel feature of these materials is that they exhibit a dual and quite unusual hysteresis loop corresponding to both the ferromagnetism and the coexisting bulk superconductivity
Pressure enhanced superconductivity at 10 K in La doped EuBiS2F
Polycrystalline Eu0.5La0.5BiS2F was synthesized by solid state reaction which
crystallizes in the tetragonal CeOBiS2 structure (P4/nmm). We report here
enhancement of Tc to 2.2 K in Eu0.5La0.5BiS2F (by electron doping in EuBiS2F
with Tc ~ 0.3 K). Eu0.5La0.5BiS2F is semiconducting down to 3 K and an onset of
superconductivity is seen at 2.2 K at ambient pressure. Upon application of
pressure the Tc could be enhanced upto 10 K. Step like features are seen in the
resistivity curves at intermediate pressures (0.5 - 1 GPa) which hints towards
the possible existence of two phases with different Tc. At a pressure above
1.38GPa, the Tconset remains invariant at 10 K but the Tc(\r{ho}=0) is
increased to above 8.2 K. There is a possible transformation from a low Tc
phase to a high Tc phase by application of pressure.Comment: Accepted in Supercond. Sci. Technol. (Sept 2015
High spin band structures in doubly-odd Tl
The high-spin states in odd-odd Tl nucleus have been studied by
populating them using the Re(C, xn) reactions at 75 MeV of
beam energy. coincidence measurement has been performed using
the INGA array with a digital data acquisition system to record the time
stamped data. Definite spin-parity assignment of the levels was made from the
DCO ratio and the IPDCO ratio measurements. The level scheme of Tl has
been extended up to 4.1 MeV in excitation energy including 19 new gamma ray
transitions. The band, in the neighboring
odd-odd Tl isotopes show very similar properties in both experimental
observables and calculated shapes. Two new band structures, with
6-quasiparticle configuration, have been observed for the first time in
Tl. One of these bands has the characteristics of a magnetic rotational
band. The cranked shell model calculations, using a deformed Woods-Saxon
potential, have been performed to obtain the total Routhian surfaces in order
to study the shapes of the bands and the band crossing in Tl. The
semiclassical formalism has been used to describe the magnetic rotational band.Comment: Accepted for publication in Physical Review
Redetermination of Sr2PdO3 from single-crystal X-ray data
The crystal structure redetermination of Sr2PdO3 (distrontium palladium trioxide) was carried out using high-quality single-crystal X-ray data. The Sr2PdO3 structure has been described previously in at least three reports [Wasel-Nielen & Hoppe (1970). Z. Anorg. Allg. Chem. 375, 209–213; Muller & Roy (1971). Adv. Chem. Ser. 98, 28–38; Nagata et al. (2002). J. Alloys Compd. 346, 50–56], all based on powder X-ray diffraction data. The current structure refinement of Sr2PdO3, as compared to previous powder data refinements, leads to more precise cell parameters and fractional coordinates, together with anisotropic displacement parameters for all sites. The compound is confirmed to have the orthorhombic Sr2CuO3 structure type (space group Immm) as reported previously. The structure consists of infinite chains of corner-sharing PdO4 plaquettes interspersed by SrII atoms. A brief comparison of Sr2PdO3 with the related K2NiF4 structure type is given