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1. Proximity effect in [Nb(1.5nm)/Fe(x)]$_{10}$/Nb(50nm) superconducting/ferromagnet heterostructures

Author

Khaydukov, Yu. N., Pütter, S., Guasco, L., Morari, R., Kim, G., Keller, T., Sidorenko, A. S., and Keimer, B.

Subjects
Condensed Matter - Superconductivity, Condensed Matter - Strongly Correlated Electrons
Abstract

We have investigated the structural, magnetic and superconducting properties of [Nb(1.5nm)/Fe(x)]$_{10}$ superlattices deposited on a thick Nb(50nm) layer. Our investigation showed that the Nb(50nm) layer grows epitaxially at 800$^\circ$C on Al$_2$O$_3$(1$\bar{1}$02) substrate. Samples grown at this condition posses a high residual resistivity ratio of 15-20. By using neutron reflectometry we show that Fe/Nb superlattices with $x<$ 4 nm form a depth-modulated FeNb alloy with concentration of iron varying between 60% and 90%. This alloy has properties of a weak ferromagnet. Proximity of this weak ferromagnetic layer to a thick superconductor leads to an intermediate phase that is characterized by co-existing superconducting and normal-state domains. By increasing the thickness of the Fe layer to $x$ = 4 nm the intermediate phase disappears. We attribute the intermediate state to proximity induced non-homogeneous superconductivity in the periodic Fe/Nb structure.

Published
2019
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3. A versatile UHV transport and measurement chamber for neutron reflectometry under UHV conditions

Author

Mohd, A. Syed, Pütter, S., Mattauch, S., Koutsioubas, A., Schneider, H., Weber, A., and Brückel, T.

Subjects
Physics - Instrumentation and Detectors
Abstract

We report on a versatile mini ultra-high vacuum (UHV) chamber which is designed to be used on the MAgnetic Reflectometer with high Incident Angle of the J\"ulich Centre for Neutron Science at Heinz Maier-Leibnitz Zentrum in Garching, Germany. Samples are prepared in the adjacent thin film laboratory by molecular beam epitaxy and moved into the compact chamber for transfer without exposure to ambient air. The chamber is based on DN 40 CF flanges and equipped with sapphire view ports, a small getter pump, and a wobble stick, which serves also as sample holder. Here, we present polarized neutron reflectivity measurements which have been performed on Co thin films at room temperature in UHV and in ambient air in a magnetic field of 200 mT and in the Q-range of 0.18 \AA$^{-1}$. The results confirm that the Co film is not contaminated during the polarized neutron reflectivity measurement. Herewith it is demonstrated that the mini UHV transport chamber also works as a measurement chamber which opens new possibilities for polarized neutron measurements under UHV conditions., Comment: 5 pages, 5 figures

Published
2017
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6. Tuning the Co/Sr stoichiometry of SrCoO2.5 thin films by RHEED assisted MBEgrowth

Author

Schöffmann, P., Pütter, S., Schubert, Jürgen, Zander, W., Barthel, J., Zakalek, P., Waschk, M., Heller, R., and Brückel, T.

Subjects
MBE, Rutherford Backscattering, This films, growth, RHEED, ddc:620, SrCoO
Abstract

Strontium cobaltite (SrCoO2.5+δ, SCO) is a fascinating material because of its topotactic structural phase transition caused by a change in oxygen stoichiometry. In the brownmillerite phase (δ = 0) it is an insulating antiferromagnet whereas in the perovskite phase (δ = 0.5) it is a conducting ferromagnet. In contrast, the impact of the varying Co/Sr stoichiometry on the structure has not yet been studied in SCO thin films. Using molecular beam epitaxy we have fabricated SCO thin films of varying Co/Sr stoichiometry. Films with Co excess exhibit a brownmillerite crystal structure with CoO precipitates within the thin film and on the surface. Co deficient films are amorphous. Only for 1:1 stoichiometry a pure brownmillerite structure is present. We find a clear dependence of the Reflection High Energy Electron Diffraction (RHEED) pattern of these thin films on the stoichiometry. Interestingly, RHEED is very sensitive to a Co excess of less than 12% while x-ray diffraction fails to reveal that difference. Hence, using RHEED, the stoichiometry of SCO can be evaluated and tuned in-situ to a high degree of precision, which allows for a quick adjustment of the growth parameters during a sample series.

Published
2020

13. Effect of interfacial interdiffusion on magnetism in epitaxial Fe$_4$N films on LaAlO$_3$ substrates

Author

Pandey, Nidhi, Pütter, S., Syed Mohd, Amir, Reddy, V. R., Phase, D. M., Stahn, J., Gupta, Ajay, and Gupta, M.

Subjects
ddc:530
Abstract

Epitaxial Fe$_4$N thin films grown on LaAlO$_3$ (LAO) substrate using sputtering and molecular beam epitaxy techniques have been studied in this work. Within the sputtering process, films were grown with conventional direct current magnetron sputtering (dcMS) and using a high power impulse magnetron sputtering (HiPIMS) process. Surface morphology and depth profile studies on these samples reveal that HiPIMS deposited film has the lowest roughness, the highest packing density, and the sharpest interface. We found that the substrate-film interface and the microstructure play a vital role in affecting the electronic hybridization and magnetic properties of Fe$_4$N films. La from the LAO substrate and Fe from the film interdiffuse and form an undesired interface. The magnetic moment (M$_s$) was compared using bulk, element-specific and magnetic depth profiling techniques. We found that M$_s$ was the highest when the thickness of the interdiffused layer was lowest and such conditions can only be achieved in the HiPIMS grown samples. The presence of a small moment at the N site was also evidenced by element-specific x-ray circular dichroism measurement in the HiPIMS grown sample. A large variation in the M$_s$ values of Fe$_4$N films found in the experimental works carried out so far could be due to such an interdiffused layer which is generally not expected to form in otherwise stable oxide substrate at a low substrate temperature ≈675 K. In addition, a consequence of substrate-film interdiffusion and microstructure resulted in the different kinds of magnetic anisotropies in Fe$_4$N films grown using different techniques. A detailed investigation of the substrate-film interface and microstructure on the magnetization of Fe$_4$N film is presented and discussed in this work.

Published
2019

15. Royal academy of medicine in Ireland international conference on homocysteine metabolism from basic science to clinical medicine: Proceedings of meeting held at Dromoland Castle, Co. Clare on July 2nd–6th, 1995

Author

Björkegren, K., Bergmark, C., de Faire, U., Mansoor, M. Azam, Svardal, A., Bostom, A. G., Roubenoff, R., Dellaripa, P., Nadeau, M. R., Sutherland, P., Wilson, P. W. F., Jacques, P. F., Selhub, J., Rosenberg, I. H., Bostom, A. G., Brosnan, J. T., Hall, B., Nadeau, M. R., Selhub, J., Bostom, A. G., Shemin, D., Lapane, K. L., Sutherland, P., Nadeau, M. R., Wilson, P. W. F., Selhub, J., Bostom, A. G., Shemin, D., Nadeau, M. R., Selhub, J., Bostom, A. G., Selhub, J., Jacques, P. F., Nadeau, M. R., Williams, R. R., Ellison, R. C., Cuskelly, G. J., McNulty, H., Strain, J. J., McPartlin, J. M., Scott, J. M., Chadefaux-Vekemans, B., Coudé, M., Aupetit, J., Kamoun, P., Coudé, M., Aral, B., Zabot, M. T., Aupetit, J., Kamoun, P., Chadefaux-Vekemans, B., Calaf, R., Ghiringelli, O., Barlatier, A., Charpiot, P., Rolland, P. H., Garçon, D., Charpiot, P., Augier, T., Chareyre, C., Rolland, P. H., Garçon, D., Chango, A., Hodez, F., Tronel, H., Nuel, G., Michel, F., Frémont, S., Méjean, L., Nicolas, J. P., Candito, M., Chambon, P., Gibelin, P., Amsellem, J., Baudouy, M., Morand, P., Candito, M., Chambon, P., Pringuey, D., Aubin-Brunet, V., Beaulieu, F., Darcourt, G., Bedoucha, P., Alchaar, H., Chatel, M., Candito, M., de Valk, H. W., van der Griend, R., Eeden, M. K. G. van, de Groot, E., Duran, M., Smeitink, J. A. M., de Klerk, J. B. C., Wittebol-Post, D., Rolland, M. -O., Haas, F. J. L. M., Meuwissen, O. J. A. Th., Banga, J. D., Poll-The, B. T., de Vries, J. I. P., Dekker, G. A., van Geijn, H. P., Huigens, P. C., Jakobs, C., von Blomberg, B. M. E., Deulofeu, R., Giralt, M., Aibar, C., Bauchet, C., Ballesta, A. M., Varela, G., Vila, N., Chamorro, A., Casals, F. J., Cremades, J. Diaz, Daly, L., Meleady, R., Graham, I., den Heijer, M., Brouwer, I. A., Gerrits, W. B. J., Bos, G. M. J., Blom, H. J., den Heijer, M., Bos, G. M. J., Koster, T., Vandenbroucke, J. P., Blom, H. J., Briët, E., Rosendaal, F. R., Fischer, G., Behrend, C., Bartholmes, P., Fermo, I., Paroni, R., Vigano, S., D’Angelo, A., Fermo, I., Paroni, R., Vigano, S., D’Angelo, A., Franken, D. G., Boers, G. H. J., Blom, H. J., Hamel, B. C. J., Franken, D. G., Boers, G. H. J., Blom, H. J., Ruijs, J. H. J., Franken, D. G., Blom, H. J., Boers, G. H. J., Tangerman, A., Guttormsen, A. B., Ueland, P. M., Refsum, H., Svarstad, E., Gao, W., Goldman, E., Jakubowski, H., Sebastio, G., Sperandeo, M. P., de Franchis, R., Andria, G., Garrow, T. A., Hladovec, J., Sommerova, Z., Písariková, A., Halsted, C. H., Villanueva, J., Chandler, C. J., Stabler, S. P., Allen, R. H., Muskhelishvili, L., James, S. J., Poirer, L., Jacobsen, D. W., Savon, S. R., DiCorleto, P. E., Jourdheuil-Rahmani, D., Rolland, P. H., Garçon, D., Joosten, E., Riezler, R., Allen, R., Joosten, E., Riezler, R., Allen, R., Marquardt, T., Ullrich, K., Harms, E., Koch, H. G., Koch, H. G., Evers, S., Grotemeyer, K. H., Vogelpohl, L., von Eckardstein, A., Ullrich, K., Deufel, T., Kraus, J., Harms, E., Kozich, V., Janosik, M., Sokolová, J., Bukovská, G., Kraus, J. P., Kluitmans, L. A. J., van den Heuvel, L. P., Stevens, E., Trubels, J. M. F., Blom, H. J., Boers, G. H. J., van Oost, B. A., Kraus, J. P., Kittner, S., Macko, R., Hebel, J. R., Rohr, J., Malinow, M. R., Upson, B., Buchholz, D., Earley, C., Johnson, C., Price, T. R., Rosario, J., Sloan, M., Stern, B., Wityk, R., Wozniak, M., Sherwin, R., Stolley, P., Kluijtmans, L., Heuvel, L. van den, Stevens, E., Trijbels, F., Blom, H., Boers, G., van Oost, B., den Heijer, M., Rozen, R., Löhrer, F., Angst, C., Fowler, B., Zaugg, M., Brunner, F., Haefeli, W. E., Nedrebø, B., Ericsson, U. -B., Ueland, P. M., Refsum, H., Lien, E. A., London, J., Paly, E., Paul, V., Paris, D., Kamoun, P., Chassé, J. F., Møller, J., Rasmussen, K., Meleady, R., Graham, I., Daly, L., Verhoef, P., Meleady, R., Graham, I., Daly, L., McMartin, K. E., Phifer, T. J., Alexander, J. S., Middlebrooks, M., Childress, L. E., Nicolas, J. P., Tronel, H., Chango, A., Fremont, S., Felden, F., Guerci, B., Creton, C., Drouin, P., Oakley, G. P., Elias, P. R. P., Hann, A. C., Curtis, C. G., Rose, F. A., Tudball, N., Parrot-Roulaud, F., Cochet, C., Catargi, B., Leprat, F., Latapie, J. -L., Perna, A. F., De Santo, N. G., Ingrosso, D., Galletti, P., Zappia, V., Parrot-Roulaud, F., Sassoust, G., Boissieras, P., Blom, H. J., Majors, A. K., Ehrhart, L. A., Pezacka, E. H., Perry, I. J., Morris, R. W., Ebrahim, S. B., Shaper, A. G., Refsum, H., Ueland, P. M., Pietrzik, K., Dierkes, J., Kroesen, M., Bung, P., Rasmussen, K., Moller, J., Rasmussen, K., Remacha, A., Garcia-Die, F., Cadafalch, J., Barceló, H. J., Parellada, H., Regland, B., Gottfries, C. -G., Andersson, M., Bagby, J., Dyrehag, L. -E., Abrahamsson, L., Ronge, E., Kjellman, B., Frosst, P., Christensen, B., Goyette, P., Rosenblatt, D. S., Genest, J., Rozen, R., Riedel, B., Ueland, P. M., Svardal, A. M., Silberberg, J., Crooks, R., Fryer, J., Ray, C., Guo, X. W., Xie, L., Dudman, N., Silberberg, J., Crooks, R., Fryer, J., Ray, C., Guo, X. W., Xie, L., Dudman, N., Silberberg, J., Crooks, R., Fryer, J., Ray, C., Guo, X., Xie, L., Dudman, N., Smith, B., Kohlman-Trigoboff, D., Simsir, S., Stabler, S. P., Allen, R. H., Strydom, A. J. C., Schlüssel, E., Preibisch, G., Elstner, E. F. E., Pütter, S., Spuijbroek, M. D. E. H., Goddijn-Wessel, T. A. W., Wouters, M. G. A. J., Molen, E. F. v. d., Blom, H. J., Boers, G. H. J., Steegers-Theunissen, R. P. M., Trijbels, J. M. F., Thomas, C. M. G., Eskes, T. K. A. B., Tsai, M. Y., Hanson, N., Key, N., Schwichtenberg, K., Garg, U., Todesco, L., Fowler, B., Pollaert, N., Haefeli, W. E., Thorand, B., Hages, M., Pietrzik, K., Bung, P., Holzgreve, W., Vila, N., Chamorro, A., Deulofeu, R., Aibar, C., Giralt, M., Ballesta, A. M., van der Mooren, M. J., Wouters, M. G. A. J., Schellekens, L. A., Eskes, T. K. A. B., Rolland, R., Blom, H. J., Put, N. v. d., Trijbels, F., Heuvel, L. v. d., Blom, H., Eskes, T., Steegers-Theunissen, R., Mariman, E., Heyer, M. d., Rozen, R., Daher, R., Van Lente, F., Vilkovsky, A. B., Maev, I. V., Richter, E. L., Kirnus, M. D., Varela-Moreiras, G., Alonso-Aperte, E., Rubio, M., Gassó, M., Deulofeu, R., Alvarez, L., Caballeria, J., Rodés, J., Mato, J. M., van Aerts, L. A. G. J. M., Peereboom-Stegeman, J. H. J. Copius, Noordhoek, J., Eskes, T. K. A. B., Molen, E. F. v. d., Spuijbroek, M. D. E. H., Eskes, T. K. A. B., Heuvel, L. P. v. d., Monnens, L. A. H., Blom, H. J., van Guidener, C., Janssen, M. J. F. M., Surachno, J., Stehouwer, C. D. A., van den Berg, M., Bierdrager, E., Rauwerda, J. A., Wilcken, B., Hammond, J., Wouters, M. G. A. J., Hamilton, C. J. C. M., Blom, H. J., Boers, G. H. J., Thomas, C. M. G., Borm, G. F., Eskes, T. K. A. B., Wang, H., Tsai, J. -C., Perrella, M. A., Yoshizumi, M., Sibinga, N. E. S., Haber, E., Chang, T. H. -T., Schlegel, R., Lee, M. -E., Woodside, J., McMaster, D., Yarnell, J., Young, I., Mercer, C., Byrne, K., Evans, A., Gey, F., Gao, X. M., Dougan, G., Wordsworth, P., McMichael, A., Young, P. B., Kennedy, D. G., Molloy, A. M., Scott, J. M., Ward, P., Naughten, E., Cahalane, S., Murphy, D., Mayne, P., Chauveau, P., Chadefaux-Vekemans, B., Coudé, M., Aupetit, J., Kamoun, P., Jungers, P., van Asselt, D. Z. B., Blom, H. J., de Wild, G. M., van Staveren, W. A., Hoefnagels, W. H. L., Naruszewicz, M., Staniewicz, A., Dziewanowski, K., Evrovski, J., Cole, D. E. C., Callaghan, Michael, Lindgren, A., Brattström, L., Hultberg, B., Verhoef, P., Hennekens, C. H., Allen, R. H., Stabler, S. P., Willett, W. C., Stampfer, M. J., Frantzen, F., Sundrehagen, E., Verhoef, P., Kok, F. J., Stampfer, M. J., Willett, W. C., Gaziano, J. M., Hennekens, C. H., Allen, R. H., Stabler, S. P., Reynolds, R. D., Hsu, R. -J., Shane, B., Robinson, K., Kottke-Marchant, K., Green, R., Gupta, A., Jacobsen, D., Robinson, K., Mayer, E., Gupta, A., Miller, D., Marchant, K., Green, R., Jacobsen, D., Greene, R., Chong, Y. -Y., Jacobsen, D., Robinson, K., Gupta, M., Sheppard, C. A., Matthews, R. G., Goyette, P., Frosst, P., Rozen, R., Verhoef, P., Kok, F. J., Kruyssen, H. A. C. M., Witteman, J. C. M., Ueland, P. M., Boushey, C., Beresford, S., Omenn, G., Motulsky, A. G., Nygard, O., Vollset, S. E., Kvale, G., Stensvold, I., Ueland, P. M., Refsum, H., Fiskerstrand, T., Ueland, P. M., Refsum, H., Bugge, K. H., Oshaug, A., Bjønnes, C. H., Refsum, H., Wu, J. T., Wu, L. L., and Wilson, L. W.

Published
1995
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19. The effect of tilted edges on the shape anisotropy and stray field coupling of uniformly magnetized rectangular elements.

Author

Pütter, S., Mikuszeit, N., Vedmedenko, E. Y., and Oepen, H. P.

Subjects
*ANISOTROPY, *MATHEMATICAL physics, *RECTANGLES, *MAGNETOSTATICS, *POISSON'S equation, *TRAPEZOIDS
Abstract

The influence of tilted edges on the magnetostatic properties of uniformly magnetized thin rectangular elements is studied. To calculate the magnetostatic energy, the Poisson equation is solved. The shape of the magnetic element is approximated by horizontally assembled thin cuboids and the solutions of Rhodes and Rowlands [Proc. Leeds Phil. Soc. 6, 191 (1954)] are utilized. A second approach is the straightforward integration of the Poisson equation taking into account the trapezoidal shape of the side faces due to the tilted edges. For an adequate number of cuboids, both methods agree very well. It is found that the shape anisotropy of a single magnetic element with tilted edges is reduced compared to that of an ideal cuboid. For a two element system the shape anisotropy competes with the magnetostatic interaction favoring a magnetization orientation parallel to the connecting line of the elements. If the elements are oriented in-line with their short axes, the easy magnetization axis switches at a critical distance between the elements. This distance increases when the elements have tilted edges. [ABSTRACT FROM AUTHOR]

Published
2009
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20. Magneto-optic Kerr effect: Incorporating the nonlinearities of the analyzer into static photometric ellipsometry analysis.

Author

Mikuszeit, N., Pütter, S., Frömter, R., and Oepen, H. P.

Abstract

A static photometric ellipsometer allows the measurement of the magneto-optic Kerr effect at a very high signal-to-noise ratio. To gain information about the state of magnetization a mathematical description of the optical components is required. This involves the use of trigonometric functions, e.g., within the Müller calculus. As these are transcendental functions the inversion of the formulae defining the final state of polarization is impossible. The commonly applied linearization is only valid for thin samples with small Kerr angles. For large Kerr angles the nonlinearity of the analyzer setup becomes important. The influence of these nonlinearities on static ellipsometry is studied analytically and numerically. A method is developed to reveal the magnetic properties with high accuracy despite of the nonlinearities due to the optical setup. The applicability of the method is demonstrated for the experimental data obtained from an ion-irradiated iron film on silicon, revealing the magnetic behavior of the investigated sample. The encountered effects are of fundamental importance for the full vectorial magnetization analysis when large Kerr signals are obtained in experiments. [ABSTRACT FROM AUTHOR]

Published
2005
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25. Probing magnetism of nanosized single-domain particle- systems

Author

Hesse, J., Pütter, S., Michele, O., Bremers, H., Hupe, O., Hartung, H., Eichler, M., and Publica

Abstract

Magnetization measurements are the "classic" experimental method to characterize systems of single domain magnetic particles. We consider such particles fixed in space so that the orientation of the magnetization vector of each particle can be influenced by an external magnetic field with respect to characteristic particle directions, i.e. easy directions in the case of anisotropy energy. The aim of this contribution is directed towards experimentalists. We will enhance the well-known idea of the "preparation" of different low temperature magnetic states (LTMS), introduce the quasi-paramagnetic state which can be reached by the PHFC (positive high field cooling) process, briefly discuss the NHFC (negative high field cooling) and other ways to reach the LTMS. Additionally, our aim is to persuade researchers to consider the susceptibility rather than the magnetization. The most interesting topic is here the pronounced susceptibility maximum which appears in a system of small single domain particles prepared in a LTMS by a PHFC process when measuring in a constant external field versus temperature. We use the susceptibility for an ideal super-paramagnet as a limiting case and consider step by step what are the influences on the susceptibility if the real particle systems exhibit magnetic anisotropy energy, particle-particle interactions and last but not least a particle size distribution.

Published
2002

29. Shallow HEMTs For Lateral Magnetic Superlattices

Author

Dinter, R., primary, Stillrich, H., additional, Heyn, Ch., additional, Pütter, S., additional, Oepen, H. P., additional, Hansen, W., additional, Frömsdorf, A., additional, Förster, S., additional, Lee, W., additional, and Nielsch, K., additional

Published
2007
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36. Etoposide toxicity on human neuroblastoma cells in vitro is enhanced by preceeding hyperthermia

Author

Heek-Romanowski, R. Van, Pütter, S., Trarbach, T., and Kremens, B.

Abstract

Thermal enhancement has been proven in vitro for the cytotoxic effect of alkylants and platinum compounds, not, however, for etoposide, which acts synergistically to these drugs. Our in vitro study on a neuroblastoma cell line confirmed previous results in other tumor models that the cytotoxicity of etoposide (12.8% as compared to untreated controls) is not enhanced by simultaneous heating to 40 or 42°C for 1 hr (11.9%), as jugded by colony forming assay. The same temperature applied 24 hr before the drug resulted in a significant decrease of colonies (6.1%). Double treatment with etoposide within a 24-hr-interval yielded a similar result (5.6%). The colony number could be further decreased by adding hyperthermia 24 hr before the second treatment (1.3%). We demonstrate in vitro that the enhancing effect of increased temperature on the cytotoxicity of etoposide on neuroblastoma cells is not absent, but depends on scheduling. The temperature range used is achievable in total body hyperthermia. Thus, our results are relevant for possible treatment of disseminated neuroblastoma. Med. Pediatr. Oncol. 36:197–198, 2001. © 2001 Wiley-Liss, Inc.

Published
2001
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37. Soliton-Mediated Magnetic Reversal in an All-Oxide-Based Synthetic Antiferromagnetic Superlattice.

Author

Zhang K, Zhernenkov K, Saerbeck T, Glavic A, Qu L, Kinane CJ, Caruana AJ, Hua E, Gao G, Jin F, Ge B, Cheng F, Pütter S, Koutsioubas A, Mattauch S, Brueckel T, Su Y, Wang L, and Wu W

Abstract

All-oxide-based synthetic antiferromagnets (SAFs) are attracting intense research interest due to their superior tunability and great potentials for antiferromagnetic spintronic devices. In this work, using the La 2/3 Ca 1/3 MnO 3 /CaRu 1/2 Ti 1/2 O 3 (LCMO/CRTO) superlattice as a model SAF, we investigated the layer-resolved magnetic reversal mechanism by polarized neutron reflectivity. We found that the reversal of LCMO layer moments is mediated by nucleation, expansion, and shrinkage of a magnetic soliton. This unique magnetic reversal process creates a reversed magnetic configuration of the SAF after a simple field cycling. Therefore, it can enable vertical data transfer from the bottom to the top of the superlattice. The physical origin of this intriguing magnetic reversal process could be attributed to the cooperation of the surface spin-flop effect and enhanced uniaxial magnetic anisotropy of the bottom LCMO layer. This work may pave a way to utilize all-oxide-based SAFs for three-dimensional spintronic devices with vertical data transfer and high-density data storage.

Published
2021
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38. Proximity effect in [Nb(1.5 nm)/Fe( x )] 10 /Nb(50 nm) superconductor/ferromagnet heterostructures.

Author

Khaydukov Y, Pütter S, Guasco L, Morari R, Kim G, Keller T, Sidorenko A, and Keimer B

Abstract

We have investigated the structural, magnetic and superconduction properties of [Nb(1.5 nm)/Fe( x )] 10 superlattices deposited on a thick Nb(50 nm) layer. Our investigation showed that the Nb(50 nm) layer grows epitaxially at 800 °C on the Al 2 O 3 (1-102) substrate. Samples grown at this condition possess a high residual resistivity ratio of 15-20. By using neutron reflectometry we show that Fe/Nb superlattices with x < 4 nm form a depth-modulated FeNb alloy with concentration of iron varying between 60% and 90%. This alloy has weak ferromagnetic properties. The proximity of this weak ferromagnetic layer to a thick superconductor leads to an intermediate phase that is characterized by a suppressed but still finite resistance of structure in a temperature interval of about 1 K below the superconducting transition of thick Nb. By increasing the thickness of the Fe layer to x = 4 nm the intermediate phase disappears. We attribute the intermediate state to proximity induced non-homogeneous superconductivity in the structure., (Copyright © 2020, Khaydukov et al.; licensee Beilstein-Institut.)

Published
2020
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39. Impact of growth kinetics on the interface morphology and magnetization in La 1/3 Sr 2/3 FeO 3 /La 2/3 Sr 1/3 MnO 3 heterostructures.

Author

Waschk M, Sarkar A, Barthel J, Voigt J, Schröder S, Zakalek P, Schmitz M, Kirby BJ, Pütter S, Schubert J, and Brückel T

Abstract

The ability to create atomically perfect, epitaxial heterostructures of correlated complex perovskite oxides using state-of-art thin film deposition techniques has generated new physical phenomena at engineered interfaces. Here we report on the impact of growth kinetics on the magnetic structure and exchange coupling at the interface in heterostructures combining layers of antiferromagnetic La 1/3 Sr 2/3 FeO 3 (LSFO) and ferromagnetic La 2/3 Sr 1/3 MnO 3 (LSMO) on (0 0 1)-oriented SrTiO 3 (STO) substrates. Two growth orders are investigated, (a) LSMO/LSFO/STO(0 0 1) and (b) LSFO/LSMO/STO(0 0 1), where the LSFO layer is grown by molecular beam epitaxy and the LSMO layer by high oxygen pressure sputtering. The interface has been investigated using electron microscopy and polarized neutron reflectometry. Interdiffusion over seven monolayers is observed in LSMO/LSFO (a) with an almost 50% reduction in magnetization at the interface and showing no exchange coupling. However, the exchange bias effect ([Formula: see text] mT at 10 K) could be realized when the interface is atomically sharp, as in LSFO/LSMO (b). Our study therefore reveals that, even for well ordered and lattice-matched structures, the kinetics involved in the growth processes drastically influences the interface quality with a strong correlation to the magnetic properties.

Published
2020
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40. Highly ordered nanostructured surfaces obtained with silica-filled diblock-copolymer micelles as templates.

Author

Frömsdorf A, Kornowski A, Pütter S, Stillrich H, and Lee LT

Subjects
Macromolecular Substances chemistry, Materials Testing, Micelles, Molecular Conformation, Particle Size, Surface Properties, Colloids chemistry, Crystallization methods, Nanostructures chemistry, Nanostructures ultrastructure, Nanotechnology methods, Polymers chemistry, Silicon Dioxide chemistry
Abstract

In this work, we present the size-controlled preparation of silica-filled micelle cores and their self-assembly behavior, which is dependent on the block lengths, different coating techniques, and substrates. Furthermore, we present a way to use these structures as templates for highly ordered magnetic nanostructures, revealed by Ar-ion milling. The resulting structures were characterized by different imaging and scattering techniques and model simulations were performed. The characterization of the obtained nanostructured surfaces has be performed with atomic force microscopy, by scanning electron microscopy, grazing-incidence X-ray small-angle scattering, and X-ray reflectivity measurements. The magneto-optical Kerr effect was utilized to investigate magnetic properties.

Published
2007
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41. Molecular analysis of homocysteic acid-induced neuronal stress.

Author

Sommer S, Hunzinger C, Schillo S, Klemm M, Biefang-Arndt K, Schwall G, Pütter S, Hoelzer K, Schroer K, Stegmann W, and Schrattenholz A

Subjects
Amino Acid Sequence, Animals, Calcium metabolism, Embryo, Mammalian cytology, Embryo, Mammalian metabolism, Hyperhomocysteinemia metabolism, Mass Spectrometry, Mice, Molecular Sequence Data, Neurons metabolism, Pluripotent Stem Cells metabolism, Cell Differentiation drug effects, Homocysteine analogs & derivatives, Homocysteine pharmacology, Neurons cytology, Pluripotent Stem Cells cytology, Proteome
Abstract

Hyperhomocysteinemia is a risk factor for vascular and neuronal lesions often observed with concomitant high levels of homocysteic acid. In contrast to homocysteine, homocysteic acid induces calcium influx into neurons, with characteristics of an excitotoxic glutamatergic agonist at elevated concentrations. On the molecular level this is correlated to fast modifications of proteins (phosphorylation and proteolysis). Within the homocysteic acid induced molecular signature we focused in more detail on phosphorylation of two proteins implicated as risk factors in schizophrenia and neurodegeneration: Dihydropyrimidinase related protein and 14-3-3 protein isoforms. Among the identified proteins there are known chaperones and oxidative metabolism enzymes, but a few are new in context of neuronal stress: Lasp-1, a vitamin D associated factor and an expressed sequence with features of a Rho GDP dissociation inhibitor. Moreover, we detect a specific proteolytic processing of heat shock protein 70 and proteindisulfide isomerase, which is abolished by vitamins (folic acid, vitamin B12, and vitamin B6), which also decrease elevated intracellular calcium levels induced by homocysteic acid.

Published
2004
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42. Does a single vitamin B-supplementation induce functional vitamin B-deficiency?

Author

Naurath HJ, Riezler R, Pütter S, and Ubbink JB

Subjects
Adult, Cystathionine blood, Cysteine metabolism, Folic Acid therapeutic use, Gas Chromatography-Mass Spectrometry, Homocysteine blood, Homocysteine metabolism, Humans, Male, Methionine metabolism, Methylmalonic Acid blood, Middle Aged, Models, Biological, Pilot Projects, Time Factors, Vitamin B 12 therapeutic use, Vitamin B 6 therapeutic use, Dietary Supplements, Vitamin B Complex therapeutic use, Vitamin B Deficiency etiology
Abstract

In a pilot study we measured the effect of three different combinations of the vitamins B6, folate and B12 on the serum concentrations of homocysteine, cystathionine and methylmalonic acid in five healthy young men without hyperhomocysteinemia. The results indicate that there are still undescribed interactions between vitamin B6 and folate, suggesting that these two vitamins should be given together to avoid depletion of the one not given. With regard to the well known metabolic pathways of methionine and cysteine, this confirms the hypothesis that a combined supplementation with the vitamins B6 and folate (and B12) is superior to folate alone in order to lower homocysteine.

Published
2001
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43. Homocysteine-induced oxidative damage: mechanisms and possible roles in neurodegenerative and atherogenic processes.

Author

Schlüssel E, Preibisch G, Pütter S, and Elstner EF

Subjects
Alanine Transaminase metabolism, Animals, Arteriosclerosis etiology, Aspartate Aminotransferases metabolism, Basidiomycota enzymology, Enzymes drug effects, Kinetics, Malate Dehydrogenase metabolism, Monophenol Monooxygenase metabolism, Myocardium enzymology, Nervous System Diseases etiology, Oxidation-Reduction, Swine, Thermus enzymology, Dihydroxyphenylalanine chemistry, Enzymes metabolism, Homocysteine chemistry, Homocysteine pharmacology, Methionine chemistry, Models, Biological, Oxidative Stress, Pyridoxal Phosphate chemistry
Abstract

Increased blood plasma concentrations of the sulphur amino acid homocysteine ("homocysteinemia") have been brought into context with neurodegenerative and arteriosclerotic symptoms and diseases. We recently reported on biochemical model reactions on the prooxidative activity of homocysteine including the desactivation of Na+/K(+)-ATPases and hemolysis of erythrocytes (Preibisch et al., 1993). In this communication we extend our model reactions including the oxidation of methionine, metabolization of pyridoxalphosphate and dihydroxyphenylalanine, desactivations of transaminases and peroxidation of low density lipoprotein.

Published
1995
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44. [Various compression methods in chronic venous insufficiency].

Author

Pütter S, Fischer H, and Schneider W

Subjects
Chronic Disease, Humans, Knee, Leg Ulcer therapy, Occlusive Dressings, Plethysmography, Thigh, Varicose Veins physiopathology, Varicose Veins therapy, Vascular Diseases therapy, Venous Pressure, Bandages, Leg blood supply, Vascular Diseases physiopathology
Published
1970

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