71 research outputs found
Effects of interdot dipole coupling in mesoscopic epitaxial Fe(100) dot arrays
The domain structure and the coercivity of epitaxial Fe(100) circular dot arrays of different diameters and separations have been studied using magnetic force microscopy (MFM) and focused magneto-optical Kerr effect (MOKE). The MFM images of the 1 ”m diameter single domain dot arrays show direct evidence of strong interdot dipole coupling when the separation is reduced down to 0.1 ”m. The coercivity of the dots is also found to be dependent on the separation, indicating the effect of the interdot dipole coupling on the magnetization reversal process
Current-induced domain wall motion including thermal effects based on Landau-Lifshitz-Bloch equation
We employ the Landau-Lifshitz-Bloch (LLB) equation to investigate
current-induced domain wall motion at finite temperatures by numerical
micromagnetic simulations. We extend the LLB equation with spin torque terms
that account for the effect of spin-polarized currents and we find that the
velocities depend strongly on the interplay between adiabatic and non-adiabatic
spin torque terms. As a function of temperature, we find non-monotonous
behavior, which might be useful to determine the relative strengths of the spin
torque terms experimentally.Comment: 20 page, 8 figure
Switching of +/-360deg domain wall states in a nanoring by an azimuthal Oersted field
We demonstrate magnetic switching between two domain wall vortex
states in cobalt nanorings, which are candidate magnetic states for robust and
low power MRAM devices. These domain wall (DW) or "twisted onion"
states can have clockwise or counterclockwise circulation, the two states for
data storage. Reliable switching between the states is necessary for any
realistic device. We accomplish this switching by applying a circular Oersted
field created by passing current through a metal atomic force microscope tip
placed at the center of the ring. After initializing in an onion state, we
rotate the DWs to one side of the ring by passing a current through the center,
and can switch between the two twisted states by reversing the current, causing
the DWs to split and meet again on the opposite side of the ring. A larger
current will annihilate the DWs and create a perfect vortex state in the rings.Comment: 5 pages, 5 figure
Suppression of the spin waves nonreciprocity due to interfacial Dzyaloshinskii Moriya interaction by lateral confinement in magnetic nanostructures
Despite the huge recent interest towards chiral magnetism related to the
interfacial Dzyaloshinskii Moriya interaction (iDMI) in layered systems, there
is a lack of experimental data on the effect of iDMI on the spin waves
eigenmodes of laterally confined nanostructures. Here we exploit Brillouin
Light Scattering (BLS) to analyze the spin wave eigenmodes of non-interacting
circular and elliptical dots, as well as of long stripes, patterned starting
from a Pt(3.4 nm)/CoFeB(0.8 nm) bilayer, with lateral dimensions ranging from
100 nm to 400 nm. Our experimental results, corroborated by micromagnetic
simulations based on the GPU-accelerated MuMax3 software package, provide
evidence for a strong suppression of the frequency asymmetry between
counter-propagating spin waves (corresponding to either Stokes or anti-Stokes
peaks in BLS spectra), when the lateral confinement is reduced from 400 nm to
100 nm, i.e. when it becomes lower than the light wavelength. Such an evolution
reflects the modification of the spin wave character from propagating to
stationary and indicates that the BLS based method of quantifying the i-DMI
strength from the frequency difference of counter propagating spin waves is not
applicable in the case of magnetic elements with lateral dimension below about
400 nm.Comment: Accepted for pubblication by: Physical Review
Vertical current induced domain wall motion in MgO-based magnetic tunnel junction with low current densities
Shifting electrically a magnetic domain wall (DW) by the spin transfer
mechanism is one of the future ways foreseen for the switching of spintronic
memories or registers. The classical geometries where the current is injected
in the plane of the magnetic layers suffer from a poor efficiency of the
intrinsic torques acting on the DWs. A way to circumvent this problem is to use
vertical current injection. In that case, theoretical calculations attribute
the microscopic origin of DW displacements to the out-of-plane (field-like)
spin transfer torque. Here we report experiments in which we controllably
displace a DW in the planar electrode of a magnetic tunnel junction by vertical
current injection. Our measurements confirm the major role of the out-of-plane
spin torque for DW motion, and allow to quantify this term precisely. The
involved current densities are about 100 times smaller than the one commonly
observed with in-plane currents. Step by step resistance switching of the
magnetic tunnel junction opens a new way for the realization of spintronic
memristive devices
Evidence for phonon skew scattering in the spin Hall effect of platinum
\u3cp\u3eWe measure and analyze the effective spin Hall angle of platinum in the low-residual resistivity regime by second-harmonic measurements of the spin-orbit torques for a multilayer of Pt|Co|AlOx. An angular-dependent study of the torques allows us to extract the effective spin Hall angle responsible for the damping-like torque in the system. We observe a strikingly nonmonotonic and reproducible temperature dependence of the torques. This behavior is compatible with recent theoretical predictions which include both intrinsic and extrinsic (impurities and phonons) contributions to the spin Hall effect at finite temperatures.\u3c/p\u3
Colorants in Cheese Manufacture: Production, Chemistry, Interactions, and Regulation
Colored Cheddar cheeses are prepared by adding an aqueous annatto extract (norbixin) to cheese milk; however, a considerable proportion (âŒ20%) of such colorant is transferred to whey, which can limit the end use applications of whey products. Different geographical regions have adopted various strategies for handling whey derived from colored cheeses production. For example, in the United States, whey products are treated with oxidizing agents such as hydrogen peroxide and benzoyl peroxide to obtain white and colorless sprayâdried products; however, chemical bleaching of whey is prohibited in Europe and China. Fundamental studies have focused on understanding the interactions between colorants molecules and various components of cheese. In addition, the selective delivery of colorants to the cheese curd through approaches such as encapsulated norbixin and microcapsules of bixin or use of alternative colorants, including fatâsoluble/emulsified versions of annatto or betaâcarotene, has been studied. This review provides a critical analysis of pertinent scientific and patent literature pertaining to colorant delivery in cheese and various types of colorant products on the market for cheese manufacture, and also considers interactions between colorant molecules and cheese components; various strategies for elimination of color transfer to whey during cheese manufacture are also discussed
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