(VO)0.09V0.18Mo0.82O3·0.54H2O microrods have been synthesized for the first time via a hydrothermal treatment of aqueous peroxomolybdic acid and vanadyl sulfate. The compound crystallizes in hexagonal rods with space group P63, and lattice constants a=10.586Å, and c=3.698Å. The single crystalline rods exhibit diameters of 1–2μm and lengths up to 45μm. A variety of techniques, including X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscope, Fourier-transform infrared spectroscopy, differential scanning calorimetry and static magnetometry were used to characterize the product.

We have studied the interplay of magnetism and superconductivity in ${\text{LaFeAsO}}_{1\ensuremath{-}x}{\text{F}}_{x}$ and $\text{Ca}{({\text{Fe}}_{1\ensuremath{-}x}{\text{Co}}_{x})}_{2}{\text{As}}_{2}$. While antiferromagnetic spin-density wave formation is suppressed and superconductivity evolves, all samples show a doping-independent strong increase in the normal-state susceptibility upon heating which appears a general feature of iron pnictides. The data provide evidence for robust local antiferromagnetic correlations persisting even in the superconducting regime of the phase diagram.

V3O7·H2O nanobelts were prepared by a hydrothermal method at 190 °C using V2O5·nH2O gel and H2C2O4·2H2O as starting agents. The obtained nanobelts have diameters ranging from 40 to 70 nm with lengths up to several micrometers. Measurements of the static magnetic susceptibility and the specific heat show a discontinuous phase transition at around T=145 K, which separates two regions of paramagnetic behavior.

We have studied the interplay of magnetism and superconductivity in LaFeAsO$_{1-x}$F$_x$ and Ca(Fe$_{1-x}$Co$_x$)$_2$As$_2$. While antiferromagnetic spin density wave formation is suppressed and superconductivity evolves, all samples show a doping independent strong increase of the normal state susceptibility upon heating which appears a general feature of iron pnictides. The data provide evidence for robust local antiferromagnetic correlations persisting even in the superconducting regime of the phase diagram.

VO2 (B) nanobelts were prepared by a hydrothermal method at 180 °C using V2O5·nH2O sol and H2C2O4·2H2O as starting agents. The obtained nanobelts have diameters ranging from 50 to 100 nm in width, 20–30 nm in thickness with lengths up to 1.5 μm. Measurements of the static magnetic susceptibility provide evidence for two phase transitions at T1 = 225 K and T2 = 290 K, respectively. Below T1, the data suggest the presence quasi-free as well as of strongly antiferromagnetic correlated spins associated to V4+-ions.

V3O7 center dot H2O nanobelts were prepared by a hydrothermal method at 190 degrees C using V2O5 center dot nH(2)O gel and H2C2O4 center dot 2H(2)O as starting agents. The nanobelts obtained have diameters ranging from 40 to 70 nm with lengths of up to several micrometers. Their morphology and structure have been characterized by XRD, SEM, TEM and IR spectroscopy. The effect of the annealing temperature on the morphology of the resulting product has been investigated. XRD and SEM showed that thermal annealing of the V3O7 center dot H2O sample in air led to the collapse of the V3O7 center dot H2O nanobelt structure and the convert into V2O5 nanobelts. For the first time V2O5 nanobelts with an ultrahigh aspect-ratio have been obtained in air. Furthermore, electrical conductivity and static magnetic susceptibility measurements have been carried out. (C) 2009 Elsevier Ltd. All rights reserved.

We present zero field and transverse field muon spin relaxation experiments on the recently discovered Fe-based superconductor LaFeAsO1-xFx (x=0.075 and x=0.1). The temperature dependence of the deduced superfluid density is consistent with a BCS s-wave or a dirty d-wave gap function, while the field dependence strongly evidences unconventional superconductivity. We obtain the in-plane penetration depth of lambda ab(0)=254(2) nm for x=0.1 and lambda ab(0)=364(8) nm for x=0.075. Further evidence for unconventional superconductivity is provided by the ratio of Tc versus the superfluid density, which is close to the Uemura line of high-Tc cuprates.

Temperature-dependent and magnetic-field-dependent measurements of the microwave surface impedance of superconducting ${\text{LaFeAsO}}_{0.9}{\text{F}}_{0.1}$ $({T}_{c}\ensuremath{\approx}26\text{ }\text{K})$ reveal a very large upper critical field $({B}_{c2}\ensuremath{\approx}56\text{ }\text{T})$ and a large value of the depinning frequency $({f}_{0}\ensuremath{\approx}6\text{ }\text{GHz})$; together with an upper limit for the effective London penetration depth, ${\ensuremath{\lambda}}_{\text{eff}}\ensuremath{\le}200\text{ }\text{nm}$, our results indicate a strong similarity between this system and the high-${T}_{c}$ superconducting cuprates.

The influence of Li-doping on the mixed-valent vanadium oxide nanotubes has been investigated using electron energy loss spectroscopy. In particular, the electron diffraction profiles and the vanadium L excitation edges have been studied. We observe that the structure of the vanadium oxide nanotubes is stable against electron transfer upon Li-doping. Excitations at the vanadium L edges show features which are associated with a reduction of the vanadium valency.

Root of a Carbon nanotube on the sub-strate with elongated catalyst particle Rolled up AlGaAs/Cr/Pt microtube Corrosion pit generated on a shot-peened Zr-based bulk metallic glass Lattice structure of a typical edge-shared chain cuprate: Li 2 CuO 2 In February 2008, a paper appeared showing superconductivity in a layered iron arse-nide material with a transition temperature (T c) of 26K[1]. This discovery has triggered an enormous amount of research activities all over the world. Meanwhile there are more than 500 papers dealing with this new class of high temperature superconductors. At first glance the story looks very similar to that of the cuprates: There are non-superconduct-ing antiferromagnetic parent compounds, as e.g. LaOFeAs, the parent compound of the so-called '1111' structure. The systems become superconducting upon doping, for example by replacing some of the oxygen in LaOFeAs by fluorine. Also the crystal structures of the new superconductors are somehow reminiscent of the cuprates, with layers of FeAs separated by spacer layers, such as LaO, where the dopants are introduced (Fig.). However , looking in more detail on the physical properties reveals pronounced differences between pnictides and cuprates. For example, the parent compounds of the pnictides are not Mott insulators but 'bad metals' with a spin density wave state [2,3]. Moreover, comparing experimental data to DFT calculations suggests that electron correlations are less important in the pnictides. On the other hand, there are good arguments, that the superconductivity in the pnictides can not be explained within the frame of a conventional electron phonon scenario. Meanwhile there is a whole family of pnictide superconductors. The highest critical temperatures are obtained by substituting La with smaller rare earths, at present the maximum T c amounts to about 54 K in the Sm based 1111 compound [4]. A simpler class of materials based on the BaFe 2 As 2 parent compound (the '122' structure, Fig. right) that does not have the LaO spacer layers also superconducts with a comparable T c [5]. More recently, superconductivity has been discovered in even simpler LiFeAs '111' and FeSe materials [6,7]. The race is therefore on, just as for the cuprates, to discover materials with increasingly higher T c. At the IFW, research on the pnictides superconductors started in April 2008 and meanwhile there are more than 20 papers on this topic dealing with (i) the synthesis of bulk materials and thin films, (ii) experimental studies of superconductivity and …

We have studied the interplay of magnetism and superconductivity in LaFeAsO$_{1-x}$F$_x$ and Ca(Fe$_{1-x}$Co$_x$)$_2$As$_2$. While antiferromagnetic spin density wave formation is suppressed and superconductivity evolves, all samples show a doping independent strong increase of the normal state susceptibility upon heating which appears a general feature of iron pnictides. The data provide evidence for robust local antiferromagnetic correlations persisting even in the superconducting regime of the phase diagram.

TT 32.1 Thu 14:00 Poster B Matrix product state approach for a two-lead, multi-level Anderson impurity model — •Andreas Holzner1,2, Andreas Weichselbaum2, and Jan von Delft2 — 1Institute for Theoretical Physics C, RWTH Aachen, D-52056 Aachen, Germany — 2Physics Department, Arnold Sommerfeld Center for Theoretical Physics, and Center for NanoScience, Ludwig-Maximilians-Universität München, D-80333 München, Germany

Magnetization data of single crystalline La4Sr10Cu24O41 are presented. In this compound, doped spin chains and undoped spin ladders are realized. The magnetization, at low temperatures, is governed by the chain subsystem with a finite interchain coupling which leads to short range antiferromagnetic spin correlations. At higher temperatures, the response of the chains can be estimated in terms of a Curie–Weiss law. For the ladders, we apply the low temperature approximation for a S=1/2 2-leg spin ladder.

A novel preparation method of MoO2.987 nanorods and the thorough investigation of their structural and magnetic properties by means of X-ray diffraction and infrared spectroscopy as well as by scanning and transmission electron microscopy are reported. MoO3−δ nanorods were prepared via hydrothermal treatment of a mixture made from molybdenum peroxide solution and oxalic acid. The presented synthesis approach is very simple, of low-cost and can be a perspective for industrial manufacturing. The resulting single crystalline nanorods exhibit diameters of 60–90nm and lengths up to several micrometers. The crystal structure was found to be orthorhombic as in α-MoO3. This agrees with our magnetization data which imply non-magnetic Mo6+ ions but show only a small amount of magnetic impurities giving rise to a weak paramagnetic response.