Coulomb Sum Rule for \u3csup\u3e4\u3c/sup\u3eHE

We determine the Coulomb sum for 4He using the world data on 4He(e,e′) and compare the results to calculations based on realistic interactions and including two-body components in the nuclear charge operator. We find good agreement between theory and experiment when using free-nucleon form factors. The apparent reduction of the in-medium GEp implied by IA-interpretation of the L/T-ratios measured in 4He(e,e′p) and 4He(e→,e′p→) is not confirmed

Writing and Reading antiferromagnetic Mn2_2Au: N\'eel spin-orbit torques and large anisotropic magnetoresistance

Antiferromagnets are magnetically ordered materials which exhibit no net moment and thus are insensitive to magnetic fields. Antiferromagnetic spintronics aims to take advantage of this insensitivity for enhanced stability, while at the same time active manipulation up to the natural THz dynamic speeds of antiferromagnets is possible, thus combining exceptional storage density and ultra-fast switching. However, the active manipulation and read-out of the N\'eel vector (staggered moment) orientation is challenging. Recent predictions have opened up a path based on a new spin-orbit torque, which couples directly to the N\'eel order parameter. This N\'eel spin-orbit torque was first experimentally demonstrated in a pioneering work using semimetallic CuMnAs. Here we demonstrate for Mn$_2$Au, a good conductor with a high ordering temperature suitable for applications, reliable and reproducible switching using current pulses and readout by magnetoresistance measurements. The symmetry of the torques agrees with theoretical predictions and a large read-out magnetoresistance effect of more than $\simeq 6$~$\%$ is reproduced by ab initio transport calculations.Comment: 5 pages, 4 figure

Superscaling and Charge-changing Neutrino Cross Sections

The superscaling function extracted from inclusive electron scattering data is used to predict high energy charge-changing neutrino cross sections in the quasi-elastic and $\Delta$ regions.Comment: 3 pages, 2 figures, to appear in the Proceedings of the 7th International Workshop on Neutrino Factories and Superbeams, Laboratori Nazionali di Frascati, Frascati (Rome), June 21 - 26, 200

Epitaxial Co2Cr0.6Fe0.4Al thin films and magnetic tunneling junctions

Epitaxial thin films of the theoretically predicted half metal Co2Cr0.6Fe0.4Al were deposited by dc magnetron sputtering on different substrates and buffer layers. The samples were characterized by x-ray and electron beam diffraction (RHEED) demonstrating the B2 order of the Heusler compound with only a small partition of disorder on the Co sites. Magnetic tunneling junctions with Co2Cr0.6Fe0.4Al electrode, AlOx barrier and Co counter electrode were prepared. From the Julliere model a spin polarisation of Co2Cr0.6Fe0.4Al of 54% at T=4K is deduced. The relation between the annealing temperature of the Heusler electrodes and the magnitude of the tunneling magnetoresistance effect was investigated and the results are discussed in the framework of morphology and surface order based of in situ STM and RHEED investigations.Comment: accepted by J. Phys. D: Appl. Phy

A high-precision polarimeter

We have built a polarimeter in order to measure the electron beam polarization in hall C at JLAB. Using a superconducting solenoid to drive the pure-iron target foil into saturation, and a symmetrical setup to detect the Moller electrons in coincidence, we achieve an accuracy of <1%. This sets a new standard for Moller polarimeters.Comment: 17 pages, 9 figures, submitted to N.I.

y scaling in electron-nucleus scattering

Data on inclusive electron scattering from A = 4, 12, 27, 56, 197 nuclei at large momentum transfer are presented and analyzed in terms of y scaling. We find that the data do scale for y 1), and we study the convergence of the scaling function with the momentum transfer Q^2 and A

c-Axis tunneling in YBa2Cu3O7-\delta/PrBa2Cu3O7-\delta superlattices

In this work we report c-axis conductance measurements done on a superlattice based on a stack of 2 layers YBa2Cu3O{7-\delta} and 7 layers PrBa2Cu3O{7-\delta} (2:7). We find that these quasi-2D structures show no clear superconducting coupling along the c-axis. Instead, we observe tunneling with a gap of \Delta_c=5.0\pm 0.5 meV for the direction perpendicular to the superconducting planes. The conductance spectrum show well defined quasi-periodic structures which are attributed to the superlattice structure. From this data we deduce a low temperature c-axis coherence length of \xi_c=0.24\pm 0.03 nm.Comment: 15 pages, 5 figures. To appear in Phys.Rev.

Brillouin light scattering study of Co2_{2}Cr0.6_{0.6}Fe0.4_{0.4}Al and Co2_{2}FeAl Heusler compounds

The thermal magnonic spectra of Co$_{2}$Cr$_{0.6}$Fe$_{0.4}$Al (CCFA) and Co$_2$FeAl were investigated using Brillouin light scattering spectroscopy (BLS). For CCFA, the exchange constant A (exchange stiffness D) is found to be 0.48 $\mu$erg/cm (203 meV A$^2$), while for Co$_2$FeAl the corresponding values of 1.55 $\mu$erg/cm (370 meV A$^2$) were found. The observed asymmetry in the BLS spectra between the Stokes and anti-Stokes frequencies was assigned to an interplay between the asymmetrical profiles of hybridized Damon-Esbach and perpendicular standing spin-wave modes, combined with the optical sensitivity of the BLS signal to the upper side of the CCFA or Co$_2$FeAl film

Efficient metallic spintronic emitters of ultrabroadband terahertz radiation

Terahertz electromagnetic radiation is extremely useful for numerous applications such as imaging and spectroscopy. Therefore, it is highly desirable to have an efficient table-top emitter covering the 1-to-30-THz window whilst being driven by a low-cost, low-power femtosecond laser oscillator. So far, all solid-state emitters solely exploit physics related to the electron charge and deliver emission spectra with substantial gaps. Here, we take advantage of the electron spin to realize a conceptually new terahertz source which relies on tailored fundamental spintronic and photonic phenomena in magnetic metal multilayers: ultrafast photo-induced spin currents, the inverse spin-Hall effect and a broadband Fabry-P\'erot resonance. Guided by an analytical model, such spintronic route offers unique possibilities for systematic optimization. We find that a 5.8-nm-thick W/CoFeB/Pt trilayer generates ultrashort pulses fully covering the 1-to-30-THz range. Our novel source outperforms laser-oscillator-driven emitters such as ZnTe(110) crystals in terms of bandwidth, terahertz-field amplitude, flexibility, scalability and cost.Comment: 18 pages, 10 figure

Precise Neutron Magnetic Form Factors

Precise data on the neutron magnetic form factor G_{mn} have been obtained with measurements of the ratio of cross sections of D(e,e'n) and D(e,e'p) up to momentum transfers of Q^2 = 0.9 (GeV/c)^2. Data with typical uncertainties of 1.5% are presented. These data allow for the first time to extract a precise value of the magnetic radius of the neutron.Comment: 10 pages, 2 figures, submitted to Physics Letters