Element-specific magnetic moments from core-absorption magnetic circular dichroism of the doped Heusler alloyCo2Cr0.6Fe0.4Al

2003

The magnetic circular dichroism (MCD) of core-level absorption (x-ray absorption spectroscopy, XAS) spectra in the soft x-ray region has been measured for the ferromagnetic Heusler alloy ${\mathrm{Co}}_{2}{\mathrm{Cr}}_{0.6}{\mathrm{Fe}}_{0.4}\mathrm{Al}$ at the Co, Fe, and Cr ${L}_{II,III}$ edges. The comparison of XAS spectra before and after in situ cleaning of polished surfaces revealed a pronounced selective oxidation of Cr in air. For clean surfaces we observed a MCD for all three elements with Fe showing the largest moment per atom. The MCD can be explained by the density of states of the $3d$ unoccupied states, predicted by linear muffin-tin orbital atomic sphere approximation. For …

Large Magnetoresistance at Room Temperature in the Off-Stoichiometric Chalcogenide Cr0.92Te.

2006

Spin polarization of magnetoresistive materials by point contact spectroscopy

2003

In the strive to find a straightforward method for determining the spin polarization, the analysis of the Andreev reflection process in point contact junctions has attracted much interest. However, the prerequisite for anevaluation of the transport spin polarization in this scheme is the existence of elastic (ballistic or diffusive) transport, which cannot be assumed a priori. We therefore also include inelastic processes in our analysis and exemplify that thermal effects can have a significant effect on data evaluation. As ferromagnetic samples with a predicted half metallic behavior and comparably low conductivity we used thin films of the double perovskite Sr 2 FeMoO 6 and bulk material …

An Inorganic Double Helix Sheathing Alkali Metal Cations: ANb2P2S12(A=K, Rb, Cs), A Series of Thiophosphates Close to the Metal-Nonmetal Boundary-Cha…

2004

The new quaternary niobium thiophosphates ANb 2 P 2 S 1 2 (A=K, Rb, Cs) have been prepared and characterized. The title compounds were synthesized by reacting Nb metal, A 2 S, P 2 S 5 , and S at 600-700°C in evacuated silica tubes. They crystallize as "stuffed" variants of the tetragonal TaPS 6 structure type in the tetragonal space group I42d with eight formula units per unit cell and lattice constants a=15.923(2) and c=13.238(3) A for CsNb 2 P 2 S 1 2 , a= 15.887(3) and c=13.132(3) A for RbNb 2 P 2 S 1 2 , and a=15.850(2) and c= 13.119(3) A for KNb 2 P 2 S 1 2 . Their structures are based on double helices formed from interpenetrating, noninteracting spiral chains of binuclear [Nb 2 S 1 2…

Investigation of a novel material for magnetoelectronics: Co2Cr0.6Fe0.4Al

2003

Heusler compounds are promising candidates for future spintronics device applications. The electronic and magnetic properties of Co2Cr0.6Fe0.4Al, an electron-doped derivative of Co2CrAl, are investigated using circularly polarized synchrotron radiation and photoemission electron microscopy (PEEM). Element specific imaging reveals needle shaped Cr rich phases in a homogeneous bulk of the Heusler compound. The ferromagnetic domain structure is investigated on an element-resolved basis using x-ray magnetic circular dichroism (XMCD) contrast in PEEM. The structure is characterized by micrometre-size domains with a superimposed fine ripple structure; the lateral resolution in these images is abo…

Properties of Co/sub 2/YZ Heusler compounds

2005

Heusler compounds of Co/sub 2/XY composition (Co/sub 2/Cr/sub 0.6/Fe/sub 0.4/Al, Co/sub 2/FeSi) offer a variety of half-metallic ferromagnetic materials. These were prepared by arc melting and comprehensively characterized by means of X-ray diffraction ( XRD), Mossbauer spectroscopy, magnetic X-ray circular dichroism spectroscopy (MXCD), superconducting quantum interference device (SQUID) magnetometry, electron spectroscopy for chemical analysis (ESCA), extended X-ray absorption fine structure (EXAFS) and Auger electron spectroscopy (AES) depth profiling. Structural disorder phenomena, magnetic hysteresis, magnetic moments, magnetic transition temperatures and Curie temperature were obtaine…

Large magnetoresistance at room temperature in the off-stochiometric chalcogenide Cr0.92Te

2006

Abstract We present the electronic and magnetic properties of the transition chalcogenide Cr0.92Te. The compound is the hexagonal counterpart to the hypothetical half-metallic ferromagnet CrTe. The off-stochiometric phase crystallizes in the hexagonal NiAs-type structure P63/mmm. New magnetotransport results show a large magnetoresistance (MR) of 5.5% at room temperature in a magnetic field of 8 T. The remarkable MR-effect can be explained with spin-dependent scattering below the Curie temperature.

Postersitzung 10: Operative Techniken

1988

Abdominale Wunddehiszenzen treten postoperativ mit einer absoluten Haufigkeit von 1–3% auf und sind mit einer Mortalitat von bis zu 35% belastet. Die postoperative Festigkeit der Abdominalaponeurose beruht bis zum 7. postoperativen Tag allein auf dem chirurgischen Faden. Die Reisfestigkeit des Wundverschlusses steigt dann durch die Wundheilungsvorgange bis zum 21. Tag schnell an. Nach einem Vierteljahr ist eine endgultige Festigkeit erreicht [2, 4]. Die vordere Bauchwand weist durch den Faserverlauf der drei seitlichen Bauchmuskeln und der sie fortsetzenden Aponeurosen eine vorwiegend quere Struktur auf (Abb. 1, 2, 3). Die Zugfestigkeit der Abdominalaponeurosen ist in querer Richtung 3mal g…

Postersitzung 11: Erektile Dysfunktion

1988

Klinische Beobachtungen haben gezeigt, das Zigarettenrauchen eine wichtige pathogenetische Rolle bei der erektilen Dysfunktion spielt. In unserer Impotenz-Sprechstunde fiel uns auf, das einige unserer Patienten mit geringgradiger arterieller Insuffizienz nach Zigarettengenus eine verminderte pharmako-induzierte Erektion erzielten. Einige dieser Patienten wurden nach Einstellung des Zigarettenkonsums wieder potent, ohne das zusatzliche Papaverin-Phentolamin-Injektionen notwendig gewesen waren. Aus diesen Beobachtungen heraus entwikkelten wir eine tierexperimentelle Studie, um den Einflus des Zigarettenrauchens auf die penile Erektion zu untersuchen.

Scanning Probe Microscopy Study of the Metal-Rich Layered Chalcogenides TaM2Te2 (M = Co, Ni)

1998

The compounds TaNi2Te2 and TaCo2Te2 have been examined by scanning tunneling and atomic force microscopy. The title phases crystallize in layered structures with metal slabs sandwiched by tellurium atoms. Scanning probe microscope images of the surfaces of these materials arise from the surface tellurium atoms anddepending on the experimental conditionscan show very different features. The images have been simulated through surface charge densities calculated within the Extended Huckel and LMTO frameworks.

Large negative magnetoresistance effects in Co2Cr0.6Fe0.4Al

2003

Abstract Materials, which display large changes in resistivity in response to an applied magnetic field (magnetoresistance) are currently of great interest due to their potential for applications in magnetic sensors, magnetic random access memories, and spintronics. Guided by striking features in the electronic structure of several magnetic compounds, we prepared the Heusler compound Co2Cr0.6Fe0.4Al. Based on our band structure calculations, we have chosen this composition in order to obtain a half-metallic ferromagnet with a van Hove singularity in the vicinity of the Fermi energy in the majority spin channel and a gap in the minority spin channel. We find a magnetoresistive effect of 30% …

Spin polarized tunneling at room temperature in a Heusler compound-a non-oxide material with a large negative magnetoresistance effect in low magneti…

2003

Summary form only given. Materials which display large changes in resistivity in response to an applied magnetic field (magnetoresistance) are currently of great interest due to their potential for applications in magnetic sensors, magnetic random access memories, and spintronics-a new kind of electronics based on spin instead of charge. Although ferromagnetic manganites show colossal magnetoresistance (CMR) effects around their Curie temperature, the low field and nearly temperature independent magnetoresistance properties important for spintronics are found only at low temperatures. Guided by striking features in the electronic structure of several magnetic compounds, we prepared the Heus…