Compact storage ring to search for the muon electric dipole moment

We present the concept of a compact storage ring of less than 0.5 m orbit radius to search for the electric dipole moment of the muon ($d_\mu$) by adapting the "frozen spin" method. At existing muon facilities a statistics limited sensitivity of d_\mu \sim 5 \times 10^{-23} \ecm can be achieved within one year of data taking. Reaching this precision would demonstrate the viability of this novel technique to directly search for charged particle EDMs and already test a number of Standard Model extensions. At a future, high-power muon facility a statistical reach of d_\mu \sim 5 \times 10^{-25} \ecm seems realistic with this setup.Comment: improved for submission; minor modification

Optical and electrical spin injection and spin transport in hybrid Fe/GaAs devices

We discuss methods for imaging the nonequilibrium spin polarization of electrons in Fe/GaAs spin transport devices. Both optically- and electrically-injected spin distributions are studied by scanning magneto-optical Kerr rotation microscopy. Related methods are used to demonstrate electrical spin detection of optically-injected spin polarized currents. Dynamical properties of spin transport are inferred from studies based on the Hanle effect, and the influence of strain on spin transport data in these devices is discussed.Comment: 5 pages, 6 figs. ICPS-28 proceedings (July'06, Vienna) for J. Appl. Phy

Magnetic properties of single-crystalline CeCuGa3

The magnetic behavior of single-crystalline CeCuGa3 has been investigated. The compound forms in a tetragonal BaAl4-type structure consisting of rare-earth planes separated by Cu-Ga layers. If the Cu-Ga site disorder is reduced, CeCuGa3 adopts the related, likewise tetragonal BaNiSn3-type structure, in which the Ce ion are surrounded by different Cu and Ga layers and the inversion symmetry is lost. In the literature conflicting reports about the magnetic order of CeCuGa3 have been published. Single crystals with the centrosymmetric structure variant exhibit ferromagnetic order below approx. 4 K with a strong planar anisotropy. The magnetic behavior above the transition temperature can be well understood by the crystal-field splitting of the 4f Hund's rule ground-state multiplet of the Ce ions

Calorimetric Evidence of Multiband Superconductivity in Ba(Fe0.925Co0.075)2As2

We report on the determination of the electronic heat capacity of a slightly overdoped (x = 0.075) Ba(Fe1-xCox)2As2 single crystal with a Tc of 21.4 K. Our analysis of the temperature dependence of the superconducting-state specific heat provides strong evidence for a two-band s-wave order parameter with gap amplitudes 2D1(0)/kBTc=1.9 and 2D2(0)/kBTc=4.4. Our result is consistent with the recently predicted s+- order parameter [I. I. Mazin et al., Phys. Rev. Lett. 101, 057003 (2008)].Comment: 4 pages, 3 figure

Spin injection from the Heusler alloy Co_2MnGe into Al_0.1Ga_0.9As/GaAs heterostructures

Electrical spin injection from the Heusler alloy Co_2MnGe into a p-i-n Al_0.1Ga_0.9As/GaAs light emitting diode is demonstrated. A maximum steady-state spin polarization of approximately 13% at 2 K is measured in two types of heterostructures. The injected spin polarization at 2 K is calculated to be 27% based on a calibration of the spin detector using Hanle effect measurements. Although the dependence on electrical bias conditions is qualitatively similar to Fe-based spin injection devices of the same design, the spin polarization injected from Co_2MnGe decays more rapidly with increasing temperature.Comment: 8 pages, 4 figure

Importance of In-Plane Anisotropy in the Quasi Two-Dimensional Antiferromagnet BaNi2_{2}V2_{2}O8_{8}

The phase diagram of the quasi two-dimensional antiferromagnet BaNi$_{2}$V$_{2}$O$_{8}$ is studied by specific heat, thermal expansion, magnetostriction, and magnetization for magnetic fields applied perpendicular to $\mathbf{c}$. At $\mu_0H^{*}\simeq1.5$ T, a crossover to a high-field state, where $T_N(H)$ increases linearly, arises from a competition of intrinsic and field-induced in-plane anisotropies. The pressure dependences of $T_N$ and $H^{*}$ are interpreted using the picture of a pressure-induced in-plane anisotropy. Even at zero field and ambient pressure, in-plane anisotropy cannot be neglected, which implies deviations from pure Berezinskii-Kosterlitz-Thouless behavior.Comment: 4 pages, 4 figure