Electronic and atomic structures of the Sr3Ir4Sn13 single crystal: A possible charge density wave material

[[abstract]]X-ray scattering (XRS), x-ray absorption near-edge structure (XANES) and extended x-ray absorption fine structure (EXAFS) spectroscopic techniques were used to study the electronic and atomic structures of the high-quality Sr3Ir4Sn13 (SIS) single crystal below and above the transition temperature (T* ≈ 147 K). The evolution of a series of modulated satellite peaks below the transition temperature in the XRS experiment indicated the formation of a possible charge density wave (CDW) in the (110) plane. The EXAFS phase derivative analysis supports the CDW-like formation by revealing different bond distances [Sn1(2)-Sn2] below and above T* in the (110) plane. XANES spectra at the Ir L3-edge and Sn K-edge demonstrated an increase (decrease) in the unoccupied (occupied) density of Ir 5d-derived states and a nearly constant density of Sn 5p-derived states at temperatures T < T* in the (110) plane. These observations clearly suggest that the Ir 5d-derived states are closely related to the anomalous resistivity transition. Accordingly, a close relationship exists between local electronic and atomic structures and the CDW-like phase in the SIS single crystal.[[notice]]補正完

Anomalous magnetic properties of Sr(2)YRuO(6)

Anomalous magnetic properties of the double perovskite ruthenate compound Sr(2)YRuO(6) are reported here. Magnetization measurements as a function of temperature in low magnetic fields show clear evidence for two components of magnetic order (T(M1)similar to 32 K and T(M2)similar to 27 K) aligned opposite to each other with respect to the magnetic-field direction even though only Ru(5+) moments can order magnetically in this compound. The second component of the magnetic order at T(M2)similar to 27 K results only in a magnetization reversal, and not in the negative magnetization when the magnetization is measured in the field-cooled (FC) mode. Isothermal magnetization (M-H) measurements show hysteresis with maximum coercivity (H(c)) and remnant magnetization (M(r)) at T similar to 27 K, corroborating the presence of the two oppositely aligned magnetic moments, each with a ferromagnetic component. The two components of magnetic ordering are further confirmed by the double peak structure in the heat-capacity measurements. These anomalous properties have significance to some of the earlier results obtained for the Cu-substituted superconducting Sr(2)YRu(1-x)Cu(x)O(6) compounds

Spin compensation in YbSr2RuO6

The magnetic properties of the double pervoskite ruthenate YbSr2RuO6 is presented here. The compound has a monoclinic structure (P2(1)/n) and shows antiferromagnetic ordering (T-N similar to 44 K) with weak ferromagnetic component resulting from the canting of the ordered moments. The magnetization data shows clear evidence for magnetic ordering as well as magnetization reversal giving rise to negative magnetization at low temperatures. The magnetization reversal is explained on the basis of spin canting on both the Ru and Yb moments that are aligned opposite to each other

Enhanced superconducting properties in FeCr(x)Se

We report an enhancement of the superconducting transition temperature (T(c)) when chromium (Cr) is substituted in excess at the iron (Fe) site (FeCr(x)Se, x = 0.01, 0.02 and 0.03). There is a corresponding increase in the superconducting volume fraction with T(c) attaining a value of 11.2 K on 2% Cr substitution when compared to a T(c) of 8.5 K for the conventional tetragonal Fe-excess sample Fe(1+x)Se. The results point to the role of chemical pressure (introduced via ionic size variation at the Fe site upon Cr substitution in excess) on superconducting properties. (C) 2011 Elsevier Ltd. All rights reserved

Magnetic, transport and thermal properties of ternary indides R2CoIn8 (R = rare earths and Y)

The magnetic properties of the R2CoIn8 series of compounds are studied. Y2CoIn8 shows a Pauli paramagnetic behaviour. Ce2CoIn8 shows a heavy fermion and Kondo behaviour. Pr2CoIn8 shows a dominating crystal field effect. The compounds with other magnetic rare earths ( R = Sm, Nd, Gd, Tb, Dy and Ho) show antiferromagnetic ordering at low temperatures with T-N = 12, 10, 33.5, 30, 17.4 and 7.6 K, respectively. Dy2CoIn8, Ho2CoIn8 and Nd2CoIn8 show metamagnetic transitions and a field- induced ferromagnetic transition at 2 K and above approximate to 82, 54 and 85 kOe respectively. Gd2CoIn8 is a strong antiferromagnet. Sm2CoIn8 shows a dominating antiferromagnetic behaviour with a ferromagnetic component at low temperatures. Tb2CoIn8 shows a ferromagnetic component at low temperatures with the possibility of superconducting behaviour below 2.5 K. The compound also shows metamagnetic transitions in the magnetic isotherm and the possibility of complicated magnetic structure below the transition temperature

Improvement in Thermoelectric Properties by Tailoring at In and Te Site in In2Te5

We study the role of substitutions at In and Te site in the thermoelectric behavior of In2Te5. Single crystals with compositions In-2(Te1-x Se (x) )(5) (x = 0, 0.05, 0.10) and Fe0.05In1.95(Te0.90Se0.10)(5) were prepared using a modified Bridgman-Stockbarger technique. Electrical and thermal transport properties of these single crystals were measured in the temperature range of 6 K to 395 K. A substantial decrease in the thermal conductivity was observed in Fe-substituted samples, attributed to enhanced phonon scattering at point defects. Marked enhancement in the Seebeck coefficient S along with concomitant suppression of the electrical resistivity rho was observed in Se-substituted single crystals. An overall enhancement of the thermoelectric figure of merit (zT) by a factor of 310 was observed in single-crystal Fe0.05In1.95(Te0.90Se0.10)(5) compared with single crystals of the parent material In2Te5

Magnetothermopower, magnetoresistance and magnetothermal conductivity in La0.95Sr0.05Co1-xMnxO3 (0.00 <= x <= 1.00)

The dependence of magnetic and thermal transport properties on charge states of Mn and Co in LaMnO3 and LaCoO3, respectively, has motivated to perform a systematic study in the La0.95Sr0.05Co1-xMnxO3 (0.00 <= x <= 1.00). Substitution of Mn at Co-site leads to a decrease in both the thermopower (alpha) and the electrical conductivity (sigma) values. However, there is a concomitant increase in the magnetothermopower (MTP) values with an increase in Mn substitution close to paramagnetic to ferromagnetic transition temperature (T-C). We observe a tunability in the sign of magnetoresistance with an increase in Mn substitution. Thermal conductivity (kappa) exhibits a weak magnetic field dependence with magnetothermal conductivity (MTC) peaking close to T-C for 0.50 <= x <= 1.00. A maximum MTP is observed close to T-C in x = 0.95 sample. The dependence of a on magnetic field is found to increase with the enhancement of T-C in the system. We conclude that Mn substitution at Co-site not only improves the T-C in the system but also increases the effect of magnetic field on thermal transport properties

Electric field controlled magnetization and transport properties of La0.7Ca0.3MnO3 ultrathin film

We have investigated the effect of electric field on the magnetization in La0.2Ca0.3MnO3 (LCMO) ultrathin film (-10 nm) by using it as the semiconductor channel material of a prototypical field effect device and SiO2 as dielectric gate. The direct magnetization measurements confirm the formation of a large ferromagnetic phase with the increase in the negative applied gate voltage. We have also shown that a large electroresistance (ER) of similar to 78% with V-g = 8 V can obtained in LCMO by using a dielectric gate by reducing the thickness of the LCMO channel. (C) 2016 Elsevier B.V. All rights reserved

Improvement of superconducting properties in Fe1+xSe0.5Te0.5 superconductor by Cr-substitution

Enhancement of superconducting transition temperature (T-c) of parent superconductor, Fe1+xSe, of `Fe-11' family by Cr-substitution for excess Fe has been motivated us to investigate the effect of Cr-substitution in optimal superconductor or Fe1+xSe0.5Te0.5 at Fe site. Here, we report structural, magnetic, electrical transport, thermal transport and heat capacity properties or Cr-substitute compounds. x-ray diffraction measurement confirms the substitution of Cr-atoms in host lattice. Magnetic and electrical transport measurements are used to explore the superconducting properties where Cr-substituted compounds show improvement in superconducting diamagnetic fraction with same T-c as undoped one Heat capacity measurement confirms the bulk superconducting properties of compounds. Thermopower measurement characterizes the type of charge carriers in normal state. (C) 2015 Elsevier Ltd. All rights reserved