Focused-ion-beam milling based nanostencil mask fabrication for spin transfer torque studies

Focused-ion-beam milling is used to fabricate nanostencil masks suitable for the fabrication of magnetic nanostructures relevant for spin transfer torque studies. Nanostencil masks are used to define the device dimensions prior to the growth of the thin film stack. They consist of a wet etch resistant top layer and an insulator on top of a pre-patterned bottom electrode. The insulator supports a hard mask and gives rise to an undercut by its selective etching. The approach is demonstrated by fabricating current perpendicular to the plane Co/Cu/Co nanopillar junctions, which exhibit current-induced magnetization dynamics.Comment: 13 pages, 3 figures, submitted to AP

Structural Phase Transition in the 2D Spin Dimer Compound SrCu2(BO3)2

A displacive, 2nd order structural phase transition at Ts=395 K from space group I`4 2 m below Ts to I 4/m c m above Ts has been discovered in the two-dimensional spin dimer compound SrCu2(BO3)2. The temperature evolution of the structure in both phases has been studied by X-ray diffraction and Raman scattering, supplemented by differential scanning calorimetry and SQUID magnetometry. The implications of this transition and of the observed phonon anomalies in Raman scattering for spin-phonon and interlayer coupling in this quantum spin system will be discussed.Comment: 13pages, 13 figure

Interlayer Exchange Coupling Mediated by Valence Band Electrons

The interlayer exchange coupling mediated by valence band electrons in all-semiconductor IV-VI magnetic/nonmagnetic superlattices is studied theoretically. A 3D tight-binding model, accounting for the band and magnetic structure of the constituent superlattice components is used to calculate the spin-dependent part of the total electronic energy. The antiferromagnetic coupling between ferromagnetic layers in EuS/PbS superlattices is obtained, in agreement with the experimental evidences. The results obtained for the coupling between antiferromagnetic layers in EuTe/PbTe superlattices are also presented.Comment: 8 pages, 6 figures, to be submitted to Phys.Rev.

Проектирование системы электроснабжения производственной базы по обслуживанию нефтяной промышленности

В выпускной работе рассматривается система электроснабжения производственной базы по обслуживанию нефтяной промышленности. Объектом исследования является прокатно-ремонтный цех производственной базы по обслуживанию нефтяной промышленности. Цель работы: Разработка системы электроснабжения производственной базы по обслуживанию нефтяной промышленности и развитие способности решать технико-экономические вопросы при проектировании систем электроснабжения. В процессе исследования проводились расчеты электрических нагрузок прокатно-ремонтного цеха и предприятия в целом, методами коэффициента расчетной активной мощности и коэффициента спроса соответственно. Произведен выбор низковольтного оборудования прокатно-ремонтного цеха и высоковольтного оборудования главной понизительной подстанции.In the graduate qualification work, the system of power supplying production base for servicing the oil industry is considered. The object of the study is a hire and repair shop of the production base for servicing the oil industry. Purpose of work: development power supplying system production base for servicing the oil industry and development of the ability to solve technical and economic issues in the design of power supplying systems. In the process of the study, calculations were made of the electrical loads of the hire and repair shop and the enterprise as a whole, using the methods of the active power factor and the demand factor, respectively. A choice of low-voltage equipment of the hire and repair shop and high-voltage equipment of the main step-down substation were made

Observation of standing spinwaves in thin Fe-films by means of Raman spectroscopy

We report on the first observation of standing spinwaves in thin evaporated Fe-films by means of Raman scattering (RS). In earlier investigations using Brillouin scattering (BS) these modes could only be observed down to a thickness dapprox. = 200 A. We were now able to extend this range down to d approx. = 120 A using BS and to a range of 40 to 80 A using RS. We find that for values of d comparable to the penetration depth of the light the scattering intensity decreases together with d. This is explained by the assumption that the scattering intensity is determined by the net magnetic moment resulting within the probing depth of the light. The mode frequencies observed by Raman scattering follow very well a D/sub ex/* d/sup -2/ relationship from which the value of the exchange parameter D/sub ex/ has been determined. With decreasing d we also observe an increasing linewidth of the standing spinwaves. This can be attributed to the increased importance of surface roughness on the damping of these modes. 8 references, 4 figures

Optimierung konventioneller und magnetooptischer Speichermedien mittels optischer Rasternahfeldmikroskopie Abschlussbericht

SIGLEAvailable from TIB Hannover: F02B257 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung, Berlin (Germany)DEGerman

Metalloxid-Barrieren: Zwischenschichtkopplung und moegliche Anwendungen in der magnetoelektronischen Sensorik Schlussbericht

SIGLEAvailable from TIB Hannover: F02B170 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung, Berlin (Germany)DEGerman

Optimierung epitaktischer Schichten von HTSL fuer mikroelektronische Anwendungen Abschlussbericht

Thin epitaxial BiSrCaCuO-HTSC films were deposited on SrTiO_3 by MBE in an atomic layer-by-layer mode in ozone atmosphere. The properties were investigated in dependence on the stoichiometry, substrate temperature, ozone pressure, deposition rate, and thickness. The maximum critical temperature was obtained as a substrate temperature of 720 C, an ozone pressure of 2*10"-"5 mbar and a growth rate of 12 nm/h. The critical current density if 1*10"6 A/cm"2 at 5 K. X-ray diffraction analysis and TEM showed that large portions of Bi-2223 exist under these growth conditions. The TEM showed also an improvement of the substrate/film-interface by starting of the fiom growth with a SrO-layer instead of a BiO-layer. STM images showed many terraces connected by atomic steps. From these films planar S-N-S-sandwich structures were grown. The current-voltage characteristics showed a quasi-particle tunnel spectrum with a zero-bias anomaly. The reduced energy gap of 3.5-4.0 in c-direction was obtained from the derivative of the I-V-characteristic. The temperature dependence of the energy gap was linear. In the (Bi, Pb)-1212 system we reached a T_c (R=0)=92 K in polycrystalline samples. The temperature behavior of the critical current density is similar to Bi-2212. Investigations of Pb-substituted Bi-2212 single crystals confirmed the higher critical current density compared to pure Bi-2212, as we have shown before for polycrystalline samples. (orig./MM)Duenne epitaktische BiSrCaCuO-HTSL-Schichten wurden mit MBE auf SrTiO_3 atomlagenweise unter Einsatz von Ozon deponiert. Die Schichteigenschaften wurden in Abhaengigkeit der Stoechiometrie, der Substrattemperatur, des Ozondruckes, der Aufwachsrate und der Schichtdicke untersucht. Eine maximale Sprungtemperatur von 83 K bei einer Substrattemperatur von 720 C, einem Ozondruck von 2*10"-"5 mbar und einer Aufwachsrate von ca. 12 nm/h wurde erreicht. Die kritische Stromdichte der Schichten betraegt 1*10"6 A/cm"2 bei 5 K. Die Analyse der Schichten mit Roentgenbeugung und TEM ergab, dass sich unter den Wachstumsbedingungen spontan relativ grosse Anteile an Bi-2223 bilden. Die TEM-Untersuchungen zeigten auch eine deutliche Verbesserung der Substrat/Schicht-Grenzflaeche, wenn die Schicht mit einer SrO- statt einer BiO-Lage begonnen wird. Das RTM zeigt auf der Oberflaeche ueberwiegend Terrassen, die durch atomare Stufen verbunden sind. Aus diesen Schichten sind planare S-N-S-Sandwich Strukturen aufgewachsen worden, deren Strom-Spannungs-Kennlinien ein Quasiteilchen-Tunnel-Spektrum mit einer Zero-Bias-Anomalie aufwiesen. Aus den abgeleiteten Kennlinien liess sich die reduzierte Energieluecke in c-Richtung zu 3.5-4.0 bestimmen, deren Temperaturabhaengigkeit linear ist. Beim (Bi, Pb)-1212-System konnte an polykristallinen Proben ein T_c (R=0) von 92 K erzielt werden. (orig./MM)SIGLEAvailable from TIB Hannover: F96B1281+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman