Coupling of pinned magnetic moments in an antiferromagnet to a ferromagnet and its role for exchange bias

The interaction between uncompensated pinned magnetic moments within an antiferromagnetic (AFM) layer and an adjacent ferromagnetic (FM) layer responsible for the existence of exchange bias is explored in epitaxially grown trilayers of the form FM2/AFM/FM1 on Cu3Au(0 0 1) where FM1 is ~12 atomic monolayers (ML) Ni, FM2 is 21–25 ML Ni, and AFM is 27 ML or 50 ML Ni~25Mn~75. Field cooling for parallel or antiparallel alignment of the out-of-plane magnetizations of the two FM layers does not make a difference for the temperature-dependent coercivity (H C), magnitude of exchange bias field (H eb), AFM ordering temperature (T AFM), and blocking temperature for exchange bias (T b). We explain this by a model in which the uncompensated pinned magnetic moments distributed within the volume of the AFM layer interact with both of the FM layers, albeit with different strength. Parallel and antiparallel coupling between the magnetization of the pinned moments and the FM layers equally exists. This leads to the experimentally observed independence of H C, H eb, as well as of T AFM and T b on the magnetization direction of the FM layers during field cooling. These results provide new and detailed insight into revealing the subtle and complex nature of the exchange bias effect

KM3NeT:a large underwater neutrino telescope in the Mediterranean Sea

High energy neutrinos produced in astrophysical processes will allow for a new way of studying the universe. In order to detect the expected flux of high energy neutrinos from specific astrophysical sources, neutrino telescopes of a scale of a km^3 of water will be needed. A Northern Hemisphere detector is being proposed to be sited in a deep area of the Mediterranean Sea. This detector will provide complimentary sky coverage to the IceCube detector being built at the South Pole. The three neutrino telescope projects in the Mediterranean (ANTARES, NEMO and NESTOR) are partners in an effort to design, and build such a km^3 size neutrino telescope, the KM3NeT. The EU is funding a 3-year Design Study; the status of the Design Study is presented and some technical issues are discussed.Comment: 4 pages, 3 figures, Prepared for the 10th International Conference on Astroparticle and Underground Physics (TAUP 2007), Sendai, Japan, 11-15 Sep 200

Theoretical study of the local atomic and electronic structure of dimetacyano azobenzene molecules on Bi (111) substrate

The present work is devoted to the local atomic and electronic structure of dimetacyano (DMC) molecules deposited on a Bi (111) substrate before and after irradiation by X-rays and UV light using density functional theory (DFT) and a theoretical analysis of the X-ray absorption near edge tructure (XANES) spectroscopy. As a result of the calculations the low-energy structure for DMC zobenzene molecules on a Bi (111) substrate was obtained.1\. Auflag

Determinants of short-period heart rate variability in the general population

Decreased heart rate variability (HRV) is associated with a worse prognosis in a variety of diseases and disorders. We evaluated the determinants of short-period HRV in a random sample of 149 middle-aged men and 137 women from the general population. Spectral analysis was used to compute low-frequency (LF), high-frequency (HF) and total-frequency power. HRV showed a strong inverse association with age and heart rate in both sexes with a more pronounced effect of heart rate on HRV in women. Age and heart rate-adjusted LF was significantly higher in men and HF higher in women. Significant negative correlations of BMI, triglycerides, insulin and positive correlations of HDL cholesterol with LF and total power occurred only in men. In multivariate analyses, heart rate and age persisted as prominent independent predictors of HRV. In addition, BMI was strongly negatively associated with LF in men but not in women, We conclude that the more pronounced vagal influence in cardiac regulation in middle-aged women and the gender-different influence of heart rate and metabolic factors on HRV may help to explain the lower susceptibility of women for cardiac arrhythmias. Copyright (C) 2001 S. Karger AG, Basel

Dynamics of magnetic domain wall motion after nucleation: Dependence on the wall energy

The dynamics of magnetic domain wall motion in the FeNi layer of a FeNi/Al2O3/Co trilayer has been investigated by a combination of x-ray magnetic circular dichroism, photoelectron emission microscopy, and a stroboscopic pump-probe technique. The nucleation of domains and subsequent expansion by domain wall motion in the FeNi layer during nanosecond-long magnetic field pulses was observed in the viscous regime up to the Walker limit field. We attribute an observed delay of domain expansion to the influence of the domain wall energy that acts against the domain expansion and that plays an important role when domains are small.Comment: Accepted for publication in Physical Review Letter

Influence of topography and Co domain walls on the magnetization reversal of the FeNi layer in FeNi/Al_2\_2O_3\_3/Co magnetic tunnel junctions

We have studied the magnetization reversal dynamics of FeNi/Al$\_2$O$\_3$/Co magnetic tunnel junctions deposited on step-bunched Si substrates using magneto-optical Kerr effect and time-resolved x-ray photoelectron emission microscopy combined with x-ray magnetic circular dichroism (XMCD-PEEM). Different reversal mechanisms have been found depending on the substrate miscut angle. Larger terraces (smaller miscut angles) lead to a higher nucleation density and stronger domain wall pinning. The width of domain walls with respect to the size of the terraces seems to play an important role in the reversal. We used the element selectivity of XMCD-PEEM to reveal the strong influence of the stray field of domain walls in the hard magnetic layer on the magnetic switching of the soft magnetic layer.Comment: 8 Pages, 7 Figure

Interplay between magnetic anisotropy and interlayer coupling in nanosecond magnetization reversal of spin-valve trilayers

The influence of magnetic anisotropy on nanosecond magnetization reversal in coupled FeNi/Cu/Co trilayers was studied using a photoelectron emission microscope combined with x-ray magnetic circular dicroism. In quasi-isotropic samples the reversal of the soft FeNi layer is determined by domain wall pinning that leads to the formation of small and irregular domains. In samples with uniaxial magnetic anisotropy, the domains are larger and the influence of local interlayer coupling dominates the domain structure and the reversal of the FeNi layer

Ferromagnetic coupling of mononuclear Fe centers in a self-assembled metal-organic network on Au(111)

The magnetic state and magnetic coupling of individual atoms in nanoscale structures relies on a delicate balance between different interactions with the atomic-scale surrounding. Using scanning tunneling microscopy, we resolve the self-assembled formation of highly ordered bilayer structures of Fe atoms and organic linker molecules (T4PT) when deposited on a Au(111) surface. The Fe atoms are encaged in a three-dimensional coordination motif by three T4PT molecules in the surface plane and an additional T4PT unit on top. Within this crystal field, the Fe atoms retain a magnetic ground state with easy-axis anisotropy, as evidenced by X-ray absorption spectroscopy and X-ray magnetic circular dichroism. The magnetization curves reveal the existence of ferromagnetic coupling between the Fe centers

Influence of NixMn1−x thickness and composition on the Curie temperature of Ni in NixMn1−x/Ni bilayers on Cu3Au(001)

We present a magneto-optical Kerr effect study of epitaxial bilayers consisting of Ni and NixMn1−x on Cu3Au(001). The bottom Ni layer, the NixMn1−x layer thickness and its chemical composition were changed and the Curie temperature of the system was determined. We focused on two different regimes of NixMn1−x composition, namely a Mn-rich with x between 0.25 and 0.5, and a Ni-rich with x around 0.7. In these two composition ranges, a NixMn1−x overlayer exhibits a different effect on the Curie temperature of the Ni layer. While Mn-rich NixMn1−x layers reduce the Curie temperature of the Ni underlayer, Ni-rich NixMn1−x layers enhance the Curie temperature with respect to the pure Ni film. This is attributed to changes in the effective thickness of the Ni layer by exchange interactions with the NixMn1−x overlayer

Snakebite Envenoming – A Combined Density Equalizing Mapping and Scientometric Analysis of the Publication History

Estimates suggest that more than 25,000 to 125,000 people die annually from snakebite envenomation worldwide. In contrast to this major disease burden, thorough bibliometric studies do not exist so far that illustrate the overall research activity over a long time span. Therefore, the NewQIS-platform conducted an analysis on snakebite envenoming using the Thomson Reuters database Web of Science. To determine and assess changes regarding the scientific activities and to specifically address the more recent situation we analyzed two time intervals (t). During the first time interval from 1900 to 2007 (t1) 13,015 publications (p) were identified. In the following period (2008–2016 = t2) 4,982 publications were identified by the same search strategy. They originate from 114 (t1) respectively 121 countries (t2), with the USA (p = 3518), Brazil (p = 1100) and Japan (p = 961) being most productive in the first period, and the USA (p = 1087), Brazil (p = 991) and China (p = 378) in the second period, respectively. Setting the publication numbers in relation to GDP/capita, Brazil leads with 92 publications per 10,000 Int$GDP/capita, followed by India with 79 publications per 10000 Int$GDP/capita (t1). Comparing the country’s publication activity with the Human Development Index level indicates that the majority of the publications is published by highly developed countries. When calculating the average citation rates (citations per published item = CR) mainly European countries show the highest ranks: From 1900–2007 Sweden ranks first with a CR = 27, followed by the Netherlands (CR = 24.8), Switzerland (CR = 23), Spain, Austria and the USA (CR = 22). From 2008 to 2016 the highest rate achieves Switzerland with a value of 24.6, followed by Belgium (CR = 18.1), Spain (CR = 16.7), Costa Rica (CR = 14.9) and Netherlands (CR = 14). Compared with this, the USA was placed at rank 13 (CR = 9,5). In summary, the present study represents the first density-equalizing map projection and in-depth scientometric analysis of the global research output on snakebites and its venoms. So it draws a sketch of the worldwide publication architecture and indicates that countries with a high incidence of snakebites and a low economical level still need to be empowered in carrying out research in this area