Highly anisotropic magnetic domain wall behavior in-plane magnetic films

We have studied nucleation of magnetic domains and propagation of magnetic domain walls (DWs) induced by pulsed magnetic field in a ferromagnetic film with in-plane uniaxial anisotropy. Different from what have been seen up to now in out-of-plane anisotropy films, the nucleated domains have a rectangular shape in which a pair of the opposite sides are perfectly linear DWs, while the other pair present zigzags. This can be explained by magnetostatic optimization, knowing that the pulse field is applied parallel to the easy magnetization axis. The field induced propagation of these two DW types are very different. The linear ones follow a creep law identical to what is usually observed in out-of-plane films, when the velocity of zigzag DWs depends linearly on the applied field amplitude down to very low field. This most unusual feature can be explained by the shape of the DW, which makes it possible to go round the pinning defects. Thanks to that, it seems that propagation of zigzag walls agrees with the 1D model, and these results provide a first experimental evidence of the 1D model relevance in two dimensional ferromagnetic thin films. Let's note that it is the effective DW width parallel to DW propagation direction that matters in the 1D model formula, which is a relevant change when dealing with zigzag DWs.Comment: 20 pages, 13 figure

Mesoscovic magnetic/semiconductor heterostructures

We report the experimental results of Fe and Fe3O4 nanostructures on GaAs(100) surfaces and hybrid Ferromagnetic/Semiconductor/Ferromagnetic (FM/SC/FM) spintronic devices. Element specific x-ray magnetic circular dichroism (XMCD) measurements have shown directly that Fe atoms on the GaAs(100)-4 x 6 surface are ferromagnetic. Within coverages of 2.5 to 4.8 ML superparamagnetic nanoclusters are formed and exhibiting strong uniaxial anisotropy, of the order of 6.0 x 10(5) erg/cm(3). The coercivities of epitaxial Fe dot arrays films grown on GaAs(100) were observed to be dependent on the separation and size of the dots indicating that interdot dipolar coupling affects the magnetization processes in these dots. In addition Fe3O4 films grown on deformed GaAs(100) substrates have been observed to form nanostripes following the topography of the substrate and magneto-optical Kerr effect (MOKE) measurements showed that these nanostripes have uniaxial magnetic anisotropy with easy axis perpendicular to the length of the nanostripes. Meanwhile the FM/SC/FM vertical device has exhibited a biasing current dependent on MR characteristics, with a maximum change of 12% in the MR observed, indicating for the first time a large room temperature spin injection and detection

On the error term in Weyl's law for the Heisenberg manifolds (II)

In this paper we study the mean square of the error term in the Weyl's law of an irrational $(2l+1)$-dimensional Heisenberg manifold . An asymptotic formula is established

catena-Poly[[(acetato-κ2 O,O′)(methanol-κO)cadmium(II)]-μ-[1,2-bis­(1H-benzimid­azol-2-yl)ethane]-κ2 N 3:N 3′-[(acetato-κ2 O,O′)(methanol-κO)cadmium(II)]-di-μ-chlorido]

In the title complex, [Cd2(CH3COO)2Cl2(C16H14N4)(CH3OH)2]n, the CdII atom is six-coordinated by one N atom from a centrosymmetric bridging 1,2-bis­(2,2′-1H-benzimidazol-2-yl)ethane (bbe) ligand, two O atoms from a chelating acetate ligand, one O atom from a methanol mol­ecule and two bridging Cl atoms in a distorted octa­hedral geometry. The CdII atoms are connected alternately by the Cl atoms and bbe ligands, leading to a chain along [001]. These chains are further linked by O—H⋯O hydrogen bonds. Intra­chain N—H⋯O hydrogen bonds are observed

Design of antipodal Vivaldi antenna with better performances for ultra wideband applications

Abstract. Two different antipodal Vivaldi antennas design with better performances are proposed. The one is a small antipodal Vivaldi antenna for a 4.1-20 GHz frequency range, and its dimension is only 34 × 50 mm 2 . Another proposed high gain antenna can achieve the maximum gain of 15.2 dBi within its operating band. Measured results of the manufactured antipodal Vivaldi antennas are in good agreement with the simulated ones. Besides the |S11|, far field radiation pattern, current distribution, phase, gain, and group delay which are important parameters of impulse distortion in ultra-wide band antenna are well analyzed. All results show that the proposed antipodal Vivaldi antennas have better performances and they are well suited for ultra-wide band communications