Superconductivity at 5.2 K in ZrTe3 polycrystals and the effect of Cu, Ag intercalation

We report the occurrence of superconductivity in polycrystalline samples of ZrTe3 at 5.2 K temperature at ambient pressure. The superconducting state coexists with the charge density wave (CDW) phase, which sets in at 63K. The intercalation of Cu or Ag, does not have any bearing on the superconducting transition temperature but suppresses the CDW state. The feature of CDW anomaly in these compounds is clearly seen in the DC magnetization data. Resistivity data is analysed to estimate the relative loss of carriers and reduction in the nested Fermi surface area upon CDW formation in the ZrTe3 and the intercalated compounds.Comment: 5 pages, 8 figure

Metamagnetic and electronic transitions in charge-ordered Nd0.50Ca0.47Ba0.03MnO3 manganite

The ABO3 type charge-ordered antiferromagnetic Nd0.50Ca0.50MnO3 (NCMO) manganite is doped at A-site by 3 % of Ba2+ for Ca2+. The resulting system, Nd0.50Ca0.47Ba0.03MnO3 (NCBMO), is studied for the effects of Ba doping on the magnetic and electronic properties. On application of magnetic field to NCBMO, strongly correlated successive sharp metamagnetic and electronic transitions are observed from antiferromagnetic-insulating to ferromagnetic-metallic state at 2.5 K. The critical magnetic field (Hc) required for metamagnetism is found to reduce drastically from 15 T for undoped NCMO to 3 T for NCBMO. On increasing the temperature, the Hc of NCBMO passes through a minimum. This behavior of Hc of NCBMO contrasts to that of NCMO. The results are discussed in context of A-site cation disorder and size

Residual resistivity ratio and its relation to the positive magnetoresistance behavior in natural multilayer LaMn2Ge2; relevance to artificial multilayer physics

Results of low temperature magnetoresistance ($\Delta\rho/\rho$) and isothermal magnetization (M) measurements on polycrystalline ferromagnetic (T_C close to 300 K) natural multilayers, LaMn_{2+x}Ge_{2-y}Si_y, are reported. It is found that the samples with large residual resistivity ratio, $\rho(300K)/\rho(4.2K)$, exhibit large positive magnetoresistance at high magnetic fields. The Kohler's rule is not obeyed in these alloys. In addition, at 4.5 K, there is a tendency towards linear variation of $\Delta\rho/\rho$ with magnetic field with increasing $\rho(300K)/\rho(4.2K$); however, the field dependence of $\Delta\rho/\rho$ does not track that of M, thereby suggesting that the magnetoresistance originates from non-magnetic layers. It is interesting that these experimental findings on bulk polycrystals are qualitatively similar to what is seen in artificially grown multilayer systems recently.Comment: 5 pages, 3 figures, separate figures. This work is a follow-up of our earlier paper in APL, Ref. : APL Vol 71, pp 2385 (1997

An insight into spin-chain magnetism through Moessbauer spectroscopic investigations in Eu-doped Ca3Co2O6 and Ca3CoRhO6

We report the results of 151Eu Moessbauer effect and magnetization measurements in the Eu-doped Ca3Co2O6 and Ca3CoRhO6, which are of great current interest in the fields of spin-chain magnetism and geometrical frustration. We find that there is a pronounced increase in the line-width of the Moessbauer spectra below a certain characteristic temperature which is well-above the one at which three-diensional ordering features set in. This unusual broadening of the spectra indicates the existence of a characteristic temperature in these 'exotic' magnetic systems, attributable to the onset of incipient one-dimensional magnetic order. This is inferred from an intriguing correlation of this characteristic temperature with the paramagnetic Curie temperature (a measure of intrachain coupling strength in these cases)

Fluctuating shells under pressure

Thermal fluctuations strongly modify the large length-scale elastic behavior of crosslinked membranes, giving rise to scale-dependent elastic moduli. While thermal effects in flat membranes are well understood, many natural and artificial microstructures are modeled as thin elastic {\it shells}. Shells are distinguished from flat membranes by their nonzero curvature, which provides a size-dependent coupling between the in-plane stretching modes and the out-of-plane undulations. In addition, a shell can support a pressure difference between its interior and exterior. Little is known about the effect of thermal fluctuations on the elastic properties of shells. Here, we study the statistical mechanics of shape fluctuations in a pressurized spherical shell using perturbation theory and Monte Carlo computer simulations, explicitly including the effects of curvature and an inward pressure. We predict novel properties of fluctuating thin shells under point indentations and pressure-induced deformations. The contribution due to thermal fluctuations increases with increasing ratio of shell radius to thickness, and dominates the response when the product of this ratio and the thermal energy becomes large compared to the bending rigidity of the shell. Thermal effects are enhanced when a large uniform inward pressure acts on the shell, and diverge as this pressure approaches the classical buckling transition of the shell. Our results are relevant for the elasticity and osmotic collapse of microcapsules.Comment: To appear in PNAS; accepted version including Supplementary Informatio