An ab-initio theoretical investigation of the soft-magnetic properties of permalloys

We study Ni80Fe20-based permalloys with the relativistic spin-polarized Korringa-Kohn-Rostoker electronic structure method. Treating the compositional disorder with the coherent potential approximation, we investigate how the magnetocrystalline anisotropy, K, and magnetostriction, lambda, of Ni-rich Ni-Fe alloys vary with the addition of small amounts of non-magnetic transition metals, Cu and Mo. From our calculations we follow the trends in K and lambda and find the compositions of Ni-Fe-Cu and Ni-Fe-Mo where both are near zero. These high permeability compositions of Ni-Fe-Cu and Ni-Fe-Mo match well with those discovered experimentally. We monitor the connection of the magnetic anisotropy with the number of minority spin electrons, Nmin. By raising Nmin via artificially increasing the band-filling of Ni80Fe20, we are able to reproduce the key features that underpin the magnetic softening we find in the ternary alloys. The effect of band-filling on the dependence of magnetocrystalline anisotropy on atomic short-range order in Ni80Fe20 is also studied. Our calculations, based on a static concentration wave theory, indicate that the susceptibility of the high permeability of the Ni-Fe-Cu and Ni-Fe-Mo alloys to their annealing conditions is also strongly dependent on the alloys' compositions. An ideal soft magnet appears from these calculations.Comment: 20 pages, 6 figure

Effects of short-range order on the electronic structure of disordered metallic systems

For many years the Korringa-Kohn-Rostoker coherent-potential approximation (KKR-CPA) has been widely used to describe the electronic structure of disordered systems based upon a first-principles description of the crystal potential. However, as a single-site theory the KKR-CPA is unable to account for important environmental effects such as short-range order (SRO) in alloys and spin fluctuations in magnets, amongst others. Using the recently devised KKR-NLCPA (where NL stands for nonlocal), we show how to remedy this by presenting explicit calculations for the effects of SRO on the electronic structure of the bcc Cu_{50}Zn_{50} solid solution.Comment: 8 pages, 6 figures, Revised versio

Low incidence of venous thrombosis in homozygous patients with NT 20210 G to a prothrombin polymorphism.

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Electrified road transport through plug-in hybrid powertrains: Compliance by simulation of CO2 specific emission targets with real driving cycles

Worldwide targets on specific CO2 emissions (g/km) seem to make the use of internal combustion engines (ICE) prohibitive when adopting conventional driving cycles concerning road transport. This research comes therefore from the necessity of an accurate analysis of the real driving habits in order to evaluate whether its implementation on an alternative powertrain, suitable to differentiate urban (local zero emissions) and extra-urban travels (highest performances of ICEs, even better than electric motors when contemplating the entire energy chain), can guarantee the compliance with specific CO2 emissions reduction legislation; this last has been introduced with the aim of containing or even erasing global emissions from the transport sector in next years. After an overview of all the main available technological alternatives, as regards powertrains, the Plug-in Hybrid (PHEV) solution has been analysed. An experimental driving cycle is proposed by combining representative cycles obtained from a previous study, based on data provided by FCA, now Stellantis, where a clustering procedure has been applied to a sample of over two-thousand real journeys made in 2015 and 2016 in all Europe with conventional automobiles; appropriate ranges of distance, time, average speed in urban and extra urban conditions, idle times and stops have been identified thanks to a statistical analysis and the cycle has been created with all of these requirements to be as similar as possible to most of daily trips by road transport. PHEV market has been examined in order to identify the components and architectures that characterize the most registered automobiles; a realistic model has therefore been created and used for the experimental cycle simulation. Simulation results show that PHEV technology has the potential to consume 69% less fuel than a conventional vehicle counterpart with a consequent reduction of 71% in emitted tank-to-wheel (TTW) tons of CO2 and significant reductions in fuel expenditure, in one year, because of the different source of energy

Oscillatory transient regime in the forced dynamics of a spin torque nano-oscillator

We demonstrate that the transient non-autonomous dynamics of a spin torque nano-oscillator (STNO) under a radio-frequency (rf) driving signal is qualitatively different from the dynamics described by the Adler model. If the external rf current $I_{rf}$ is larger than a certain critical value $I_{cr}$ (determined by the STNO bias current and damping) strong oscillations of the STNO power and phase develop in the transient regime. The frequency of these oscillations increases with $I_{rf}$ as $\propto\sqrt{I_{rf} - I_{cr}}$ and can reach several GHz, whereas the damping rate of the oscillations is almost independent of $I_{rf}$. This oscillatory transient dynamics is caused by the strong STNO nonlinearity and should be taken into account in most STNO rf applications.Comment: 4 page, 3 figure