Anisotropic Colossal Magnetoresistance Effects in Fe_{1-x}Cu_xCr_2S_4

A detailed study of the electronic transport and magnetic properties of Fe$_{1-x}$Cu$_x$Cr$_2$S$_4$ ($x \leq 0.5$) on single crystals is presented. The resistivity is investigated for $2 \leq T \leq 300$ K in magnetic fields up to 14 Tesla and under hydrostatic pressure up to 16 kbar. In addition magnetization and ferromagnetic resonance (FMR) measurements were performed. FMR and magnetization data reveal a pronounced magnetic anisotropy, which develops below the Curie temperature, $T_{\mathrm{C}}$, and increases strongly towards lower temperatures. Increasing the Cu concentration reduces this effect. At temperatures below 35 K the magnetoresistance, $MR = \frac{\rho(0) - \rho(H)}{\rho(0)}$, exhibits a strong dependence on the direction of the magnetic field, probably due to an enhanced anisotropy. Applying the field along the hard axis leads to a change of sign and a strong increase of the absolute value of the magnetoresistance. On the other hand the magnetoresistance remains positive down to lower temperatures, exhibiting a smeared out maximum with the magnetic field applied along the easy axis. The results are discussed in the ionic picture using a triple-exchange model for electron hopping as well as a half-metal utilizing a band picture.Comment: some typos correcte

Spiral spin-liquid and the emergence of a vortex-like state in MnSc2_2S4_4

Spirals and helices are common motifs of long-range order in magnetic solids, and they may also be organized into more complex emergent structures such as magnetic skyrmions and vortices. A new type of spiral state, the spiral spin-liquid, in which spins fluctuate collectively as spirals, has recently been predicted to exist. Here, using neutron scattering techniques, we experimentally prove the existence of a spiral spin-liquid in MnSc$_2$S$_4$ by directly observing the 'spiral surface' - a continuous surface of spiral propagation vectors in reciprocal space. We elucidate the multi-step ordering behavior of the spiral spin-liquid, and discover a vortex-like triple-q phase on application of a magnetic field. Our results prove the effectiveness of the $J_1$-$J_2$ Hamiltonian on the diamond lattice as a model for the spiral spin-liquid state in MnSc$_2$S$_4$, and also demonstrate a new way to realize a magnetic vortex lattice.Comment: 10 pages, 11 figure

Attractive van-der-Waals energies between BMP-2 and the graphite surface.

<p>Attractive van-der-Waals energies between BMP-2 and the graphite surface.</p

Snapshot of the BMP-2 molecule (orientation 1) after 20 ns. a) cMD; b) aMD with sideview (left) and topview (right).

<p>Snapshot of the BMP-2 molecule (orientation 1) after 20 ns. a) cMD; b) aMD with sideview (left) and topview (right).</p

Simulation of water droplet on graphite surface and fit (black circle) through the droplet surface above 8 Å (red) to exclude the near wall region (blue) according to

<p><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0064883#pone.0064883-Werder1" target="_blank">[<b>27</b>]</a><b>.</b> The green line represents the tangent to the fitted droplet surface in order to determine the contact angle.</p

Secondary structure of BMP-2 before adsorption and at the end of the simulation calculated with dssp [43].

<p>Secondary structure of BMP-2 before adsorption and at the end of the simulation calculated with dssp <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0064883#pone.0064883-Kabsch1" target="_blank">[43]</a>.</p

Conformational space obtained by projection of the trajectory onto the first two eigenvectors of the protein atom covariance matrix.

<p>Each point represents a conformational state at a simulation time shown by the color code.</p